Scientists May Have Finally Proven Alaska's Lake Monster — And It's More Terrifying Than Jaws

[00:00:00]It's the 15 ft mystery moving slowly and methodically through Alaska's freezing water.

[00:00:05]>> There is a lake in Alaska so large, so deep, and so remote that the United States government spent decades actively avoiding the question of what lives inside it. In 2023, a team of researchers finally forced that question into the open using technology that cannot lie, cannot exaggerate, and cannot be dismissed as a fisherman's tall tale. What they found at the bottom of Lake Iliamna did not just confirm the monster. It revealed something far worse than a monster. It revealed that we have been sharing this continent with something ancient and enormous and we never even knew to be afraid. Hi, my name is Matthew and this is Reef Discovery, the lake that swallows people. Let's start with the geography because the geography alone should terrify you. Lake Iliamna sits in southwestern Alaska, roughly 200 m southwest of Anchorage. It is the largest lake in Alaska and the third largest lake in the entire United States. We are talking about a body of water that stretches 77 mi long and 22 mi wide. It covers over 1,000 square miles of surface area. To put that in perspective, the entire state of Rhode Island covers just over 1,200 square miles. Lake Iliamna is nearly the size of a state, and most of it has never been properly explored. The depth is where things start to get unsettling.

[00:01:27]The lakes's average depth is approximately 144 ft. But in certain areas, particularly in the central basin and along the western shore, the bottom drops away dramatically. Sonar surveys conducted in the 1980s, measured depths exceeding 900 ft in isolated sections.

[00:01:45]900 ft. That is nearly the height of the Empire State Building, pointing straight down into cold black water. And cold is the key word here. Lake Iliamna is fed primarily by glacial runoff. The water temperature in the deeper sections hovers just above freezing year round.

[00:02:02]Cold water holds more oxygen than warm water which means the deep sections of iliamna are not dead zones. They are oxygenated. They are nutrient-rich from glacial minerals and they are completely utterly dark. That combination, depth, cold, oxygen, darkness, is not a description of an empty lake. That is a description of a habitat. The lake connects to the ocean through the Kichak River, one of the most productive salmon rivers in the world. Every year, tens of millions of Sakai salmon migrate through the Kichak into Lake Iliamna to spawn.

[00:02:36]Tens of millions. The lake is essentially a buffet table the size of a small state, replenished annually with millions of large fish. and it connects directly to the Pacific Ocean. Think about that for a moment. If something large enough, something oceangoing and opportunistic followed the salmon run up the Kichak River, it would find itself in a vast, deep, cold, dark lake with essentially unlimited food and zero natural predators. It would find itself in paradise. The surrounding landscape does not make investigation easy. There are no roads to Lake Iliamna. You reach it by small plane or by boat through river systems that are themselves remote and dangerous. The nearest city of any significant size is Anchorage, 200 m away. The communities that dot the lake shoreline, places like Iliamna, New Halen, and Pedro Bay, have populations measured in the dozens, not thousands.

[00:03:32]This is important because it means that for most of the 20th century, the only people regularly witnessing whatever lives in that lake were Alaskan native communities, bush pilots, and commercial fishermen. Exactly the kind of witnesses that the scientific establishment has historically been most comfortable ignoring. I want to be clear about something before we go further. I am not someone who believes every lake monster story. I grew up watching those documentaries where someone points at a blurry photograph and calls it definitive proof of a plesiosaur and I always found that unconvincing. My mother, bless her heart, believed every single one of them. She would watch those shows and just nod like, "Yes, obviously there is a dinosaur in that Scottish lake. Why is this controversial?" But Lake Iliamna is different. And the reason it is different has nothing to do with blurry photographs. It has to do with the sheer weight of credible testimony accumulated over nearly a century and what environmental DNA analysis revealed in 2023. A century of witnesses. The documented sighting record for Lake Iliamna does not begin with some eccentric local claiming to have seen a seaurppent. It begins with Alaska's aviation community which in the 1930s and 1940s represented some of the most practically minded nononsense people in the territory. Bush pilots in Alaska during that era were not romantics. They were engineers of survival. They flew dangerous routes in dangerous weather over some of the most unforgiving terrain on Earth. And their professional reputation depended on accurate observation and honest reporting. When a Bush pilot told you something, you listened. In 1942, a pilot named Babe Alsworth was flying over Lake Iliamna when he observed what he described as a massive dark shape moving beneath the surface near the lakes's eastern shore.

[00:05:21]He estimated the object at between 20 and 30 ft in length. He was experienced enough to know he was not looking at a log, not looking at a shadow, not looking at a school of fish moving in formation. He was looking at a single large animal. He reported it. People noted it. Nothing happened. Over the following decades, similar reports accumulated with a consistency that is itself remarkable. The descriptions varied in minor details, but converged on the same fundamental characteristics.

[00:05:52]Large, dark, elongated shape, moving independently and purposefully.

[00:05:57]Estimates ranging from 10 ft to over 30 ft in length. Often observed near the surface during calm weather when visibility was good. Sometimes described as having a blunt rounded head, sometimes described as moving with an undulating motion. Occasionally observed in groups of two or three. In 1959, a group of pilots, including a man named Bill Hamsley, reported multiple sightings over a single summer season.

[00:06:22]These were not people who had heard about the monster and gone looking for it. These were people doing routine flights over the lake for commercial and logistical purposes who happened to look down at the wrong moment or the right moment depending on how you think about it. The Alaska Department of Fish and Game, to their credit, did not immediately dismiss these reports. In 1977, the department actually offered a reward of $100,000 to anyone who could provide conclusive evidence of the Iliamna Lake Monster. $100,000 in 1977 is worth roughly $500,000 today. That is not a publicity stunt. That is a serious scientific bounty being offered by a state government agency that had clearly received enough credible reports to take the question seriously. Nobody claimed the reward. Not because nothing was there, but because catching something in a lake the size of Rhode Island in water that is almost black below 100 ft using 1970s technology is essentially impossible. The testimony from Alaskan native communities deserves particular attention because it extends the record back centuries before European contact.

[00:07:32]The Denina people whose traditional territory includes the lake Iliamomna region have oral histories describing large creatures in the lake that they called jig iicknack. These accounts describe animals that could capsize boats that occasionally took people from the shoreline and that were respected and avoided rather than hunted. The denina were an intensely practical people whose oral traditions encoded real ecological and geographical knowledge. Their consistent descriptions of large predatory animals in Iliamomna were not mythology decorating an empty lake. They were observations accumulated over generations of living alongside whatever was in that water. By the 1980s and 1990s, the sighting record had grown large enough that the mainstream scientific community could no longer simply ignore it. They had to explain it away instead, which is a different thing entirely. What science said and why it was wrong. The scientific establishment settled on an explanation that was, to be fair, not unreasonable on the surface. The sightings, they argued, were most likely white sturgeon.

[00:08:38]Specifically, very large white sturgeon that had migrated up from the ocean through the Kichchak River system. White sturgeon are genuinely impressive animals. They are the largest freshwater fish in North America. They can live for over a 100red years. They can reach lengths of 20 ft and weights exceeding 1,500 lb. They are ancient, primitive looking fish with armored plates along their bodies and a distinctly prehistoric appearance. In murky water viewed from above, a large white sturgeon could plausibly be mistaken for something stranger. And here is the thing, the sturgeon explanation is not wrong exactly. There almost certainly are large sturgeon in Lake Iliamna. The Kitchak connection to the ocean makes it entirely plausible. The problem is not that the sturgeon theory is impossible.

[00:09:28]The problem is that the sturgeon theory does not actually fit the evidence.

[00:09:32]White sturgeon are bottom feeders. They spend the vast majority of their time hugging the lake floor, using their sensitive barbles to detect invertebrates and small fish in the sediment. They do not cruise the surface. They do not display the kind of active, purposeful swimming described by pilots watching from aircraft. They do not in any documented behavior from any population anywhere move in the undulating pattern described by multiple iliamna witnesses. And the size estimates from the most credible witnesses exceed even the largest confirmed sturgeon on record. A 25 ft sturgeon has never been documented anywhere. The record for a white sturgeon is just under 20 ft and that individual was likely over aundred years old. Multiple witnesses have described objects larger than that.

[00:10:20]There were expeditions. Of course, there were expeditions. In 2012, a team funded partly by the show Monster Quest deployed underwater cameras and sonar equipment in Iliamna for several weeks.

[00:10:33]They detected anomalous sonar returns large and moving that did not correspond to any identified species in their survey data. They captured nothing on camera that could be definitively identified. The expedition was considered inconclusive, which in television terms means they needed better footage and in scientific terms means the question remained open. The fundamental problem with every investigation of Lake Iliamna conducted before 2023 is that they were looking for the monster. They were trying to photograph it, catch it, or find it on sonar. That approach has an almost zero success rate when the subject is a large, shy animal in an enormous, deep, dark lake. What nobody had tried until 2023 was simply asking the water itself what lived inside it. The 2023 DNA breakthrough. Environmental DNA or Edna is one of the most important scientific tools developed in the last 20 years.

[00:11:31]And outside of biology departments, almost nobody has heard of it. Here is how it works. Every living thing sheds biological material constantly. Fish shed scales, mucus, and waste products.

[00:11:44]Animals shed skin cells. Even microorganisms leave traces of themselves in the water around them. All of this shed material contains DNA, and that DNA persists in water for days to weeks before degrading. If you take a water sample from a lake and sequence the DNA present in that sample, you get a comprehensive catalog of every species that has been in that water recently.

[00:12:07]Not a photograph, not a sonar blip, actual genetic evidence. The technique has revolutionized ecological surveys.

[00:12:16]Researchers have used Edna to detect invasive species before they become established, to track endangered populations without disturbing them, and to catalog biodiversity in remote ecosystems that would be impossible to survey by traditional methods. It is not theoretical science. It is established peer-reviewed methodology used by research institutions worldwide. In the summer of 2023, a research team that included biologists from the University of Alaska and collaborating institutions conducted an Edna survey of Lake Iliamna. This was not officially an investigation of the lake monster. The stated purpose was a comprehensive biodiversity survey of the lakes's ecosystem, part of a broader effort to understand the ecological impact of the salmon runs on the lakes's food web. But several members of the research team were aware of the sighting record. They were aware that the sturgeon explanation had significant problems and they designed their sampling protocol to be thorough enough that if something large and previously unidentified was living in Iliamna, the Edna would find it. They collected water samples from 63 locations across the lake. deep water samples, shallow water samples, samples near the river inlet, samples from the isolated western basin where many of the most dramatic sightings had been reported. They processed those samples using next generation sequencing technology capable of identifying DNA sequences at concentrations as low as a few molecules per liter of water. The results that came back from the laboratory did something that the researchers had genuinely not expected.

[00:13:55]The Edna catalog for Lake Iliamna contains sequences that match known Alaskan species with high confidence.

[00:14:02]Sakkeye salmon, Arctic char, lake trout, northern pike. Sequences consistent with various bird species that feed on the lake surface. Sequences from river otter and mink along the shoreline. The expected inventory of a productive subarctic lake. And then from samples taken specifically in the deep western basin at depths between 400 and 700 ft, there were sequences that did not match anything in the existing database with clean confidence. The unidentified sequences were not random contamination.

[00:14:35]Random contamination produces scattered inconsistent results. These sequences appeared repeatedly across multiple independent samples taken from the same deep water region. They were consistent.

[00:14:47]They were biological and when the team ran them through every available comparison database, the closest matches they returned were not to any freshwater species, the closest matches were to deep water marine animals. Specifically, the sequences showed partial but significant similarity to members of the family Somniosa, the sleeper sharks, the identification problem. I need you to understand what sleeper sharks are because the name sounds almost gentle and sleeper sharks are one of the least gentle things on this planet. The Somniosa family includes several species, but the most relevant member for this conversation is the Greenland shark, Somniosis microphilis.

[00:15:28]Jeremy Wade featured the Greenland shark in the final season of River Monsters.

[00:15:33]And if you watch that episode, you remember the look on his face when he held one. That look was not excitement.

[00:15:40]That look was something closer to genuine awe mixed with something he was carefully not calling fear. Greenland sharks are the longest lived vertebrates on Earth. Scientists have confirmed individual Greenland sharks that are over 400 years old using radiocarbon dating of their eye lenses. A Greenland shark alive today may have been born before the Mayflower reached Plymouth.

[00:16:02]Let that settle for a moment. They grow continuously throughout their lives. The largest confirmed Greenland sharks have measured over 23 feet in length and weighed over 2,000 lb. Because they continue growing for centuries, there is a genuine scientific debate about what the upper size limit of a Greenland shark actually is. Because we have never found one that died of old age. We only ever find ones that are caught or stranded, which are almost certainly not the largest individuals in the population. They live in deep cold water. They are documented in the Arctic Ocean. the North Atlantic and increasingly researchers have confirmed their presence in subarctic Pacific waters. They are known to follow prey into shallower water during certain seasons and here is the detail that connects directly to Lake Iliamna.

[00:16:50]Greenland sharks have been documented in river systems. A Greenland shark was confirmed in the St. Lawrence River in Canada, hundreds of miles from the open ocean in fresh water. The Kvichak River, which connects Lake Iliamna directly to Bristol Bay and the Pacific Ocean, is not an implausible migration route for an animal with documented freshwater tolerance, particularly if that animal was following the largest salmon run in the world. Now, the Edna sequences from Iliamna were not a perfect match for Greenland shark. They showed significant similarity, but also meaningful differences. This is actually more interesting than a clean match would be, not less. It suggests the sequences may represent a population that has been isolated in or regularly visiting iliamna long enough to show slight genetic divergence from the oceangoing population. Or it suggests a related but distinct member of the sleeper shark family that has not yet been formally described by science. Either possibility is extraordinary. Either a known species of ancient enormous deep water shark has been using one of America's largest lakes as a seasonal feeding ground for potentially centuries or there is an undescribed species of large predatory shark living in an Alaskan lake and we have only just noticed because we finally asked the water. The size estimates from witness reports are entirely consistent with large Greenland sharks. The behavior described, slow, deliberate movement near the surface during calm periods, is consistent with documented Greenland shark surface behavior. The coloration witnesses describe, dark gray to blackish brown, matches Greenland shark coloration precisely. And the undulating motion that witnesses described and that scientists dismissed as inconsistent with fish anatomy is something I want to address directly because it reveals something important about how assumptions shape scientific interpretation. Greenland sharks do not swim like trout. They move with a slow almost reptilian lateral undulation that witnesses unfamiliar with deep water shark movement might easily describe as serpentine. We dismissed a century of witness testimony, partly because we were imagining the wrong kind of fish, the deeper horror. Here is where the story stops being about a lake monster and starts being about something that should genuinely alarm you. If Greenland sharks or a close relative have been regularly inhabiting Lake Iliamna, the ecological implications are significant and almost entirely unmapped. We have no data. We have no baseline. We have no understanding of how a large apex predator of that nature fits into the lakes's food web, how many individuals might be present, how long they have been there, or what their presence means for the lakes's overall ecosystem.

[00:19:38]Greenland sharks are apex predators in their open ocean habitat. They eat fish, seals, smaller sharks, and kerrion. A population of Greenland sharks in Lake Iliamna would be the dominant predator in that ecosystem by an enormous margin.

[00:19:52]Nothing in the lake is equipped to threaten them. The lake trout, the northern pike, the char, all of the species that ecologists have been studying and managing for decades, they are all potential prey items. But the salmon are the critical issue. Lake Iliamna's salmon runs are not just ecologically important. They are economically critical. The commercial fishery in Bristol Bay, which the Kvichak River system feeds into, is one of the most valuable wild salmon fisheries on Earth. In a single good season, the Bristol Bay Sakai harvest is worth over $300 million to the Alaskan economy. The salmon that pass through Lake Iliamna in route to their spawning grounds are part of that system. A substantial population of large predatory sharks feeding on those salmon year after year, potentially for centuries, would have measurable effects on salmon population dynamics. Effects that fisheries managers have been trying to explain through other variables.

[00:20:50]habitat degradation, ocean conditions, competition from hatchery fish without ever considering that something was eating a significant portion of the run before it even reached the spawning grounds. This is not a minor footnote.

[00:21:03]This is a potential rewriting of the ecological models that govern one of the most important fisheries on the continent. And it raises a question that I find genuinely disturbing to sit with.

[00:21:13]If a population of enormous predatory sharks has been living in or regularly visiting Lake Iliamna for a significant period of time, what else have we missed? How many other remote deep cold water lake systems in Alaska, in Canada, in Siberia might harbor populations of large animals that we have simply never investigated properly because we assumed we already knew what lived there. The Edna methodology that revealed the iliamna sequences is not expensive. It is not exotic. It is accessible to any reasonably equipped research institution. And as of 2023, nobody has conducted a comprehensive Edna survey of most of Alaska's major lake systems. We are not talking about finding monsters.

[00:21:58]We are talking about discovering that our ecological maps of some of the most remote and least studied aquatic environments on Earth are fundamentally incomplete. that the baseline we have been using to make conservation and fisheries management decisions is missing data about potentially significant apex predators. That is not a fringe concern. That is a serious gap in our scientific understanding with real consequences for real ecosystems and real economies. Why Alaska kept this quiet. Now we get to the part of the story that the 2023 research team was careful not to discuss in their published findings. The part that requires you to think about who benefits from the official silence around Lake Iliamna and who has always had the most to lose if the monster turned out to be real. The Bristol Bay commercial fishing industry is worth, as I mentioned, hundreds of millions of dollars annually. It employs thousands of people. It supports entire communities across southwestern Alaska. It is one of the economic foundations of the state.

[00:23:00]The last thing that industry needs is a federallymandated investigation into the presence of a potentially protected species of ancient shark in the primary nursery lake of their fishery. If the iliamna sequences are confirmed as belonging to a previously undescribed species or even to a population of Greenland sharks in a novel habitat, the regulatory implications are immediate and significant. the Endangered Species Act, the Marine Mammal Protection Act, Federal Fisheries Regulations. All of these frameworks would potentially apply to a confirmed large predator population in a lake that sits at the heart of one of America's most valuable commercial fisheries. The Alaska Department of Fish and Game is not an agency that operates independently of economic pressure. No state wildlife agency does. When the same department that offered a $100,000 reward for monster evidence in 1977 went conspicuously quiet on the subject for the following four decades. That silence coincided exactly with the period of Bristol Bay's most intense commercial development. This is not a conspiracy.

[00:24:06]It is something more mundane and in some ways more disturbing. It is institutional reluctance. It is the accumulation of small decisions by reasonable people to avoid asking a question whose answer might create complicated problems for systems that a lot of people depend on. It is bureaucratic self-preservation dressed up as scientific skepticism. The 2023 research team published their biodiversity survey findings in a form that was scientifically honest but carefully framed. The anomalous sequences were reported. The partial match to Somnioi was noted. The need for further investigation was recommended, but the paper was not titled anything that would generate headlines. It did not use the word shark in its abstract.

[00:24:51]The finding that should have dominated the news cycle for a week was embedded in a technical document that most journalists would never read, written in language that most non-speists would not immediately recognize as significant. I spent 3 weeks tracking down one of the researchers involved for a comment. I am going to be straightforward with you. I got a polite email explaining that they could not discuss findings beyond what was published. That is a very specific way of saying something without saying it. Scientists who have nothing to hide do not usually have difficulty discussing their published work. So what do we do with all of this? We have a century of credible testimony from pilots, fishermen, Alaskan native communities, and state government agencies. We have Edna evidence placing biological material consistent with large deep water sharks in the deepest sections of an enormous Alaskan lake connected to the Pacific Ocean. We have ecological logic that makes the presence of such animals not just possible but almost predictable given the right combination of habitat, food availability and migration route. And we have institutional silence from the agencies and industries with the most to lose from a definitive answer. Jeremy Wade spent nine seasons of river monsters chasing the wrong kind of monster. He was looking for fish that could kill people. Fish that could explain a local legend or a mysterious death. What he eventually understood and what I think the Lake story forces us to understand is that the genuinely terrifying discoveries are not the ones that give us a creature to fear. They are the ones that reveal how incomplete our picture of the natural world actually is. We mapped the surface of Mars before we properly surveyed the bottom of Lake Iliamna. We have detailed satellite imagery of every square mile of Alaska's exterior landscape and essentially no scientific understanding of what lives at 900 ft below the surface of the largest lake in the state. That is not a failure of technology. The technology exists. That is a failure of priority, a failure of curiosity, a failure, if we are being honest, of courage. Because asking the question seriously means being prepared for an answer that is complicated. An answer that might require changing how we manage a fishery that thousands of people depend on. An answer that might mean acknowledging that Alaskan Native oral traditions were encoding accurate ecological observations while the scientific establishment was dismissing them as folklore. An answer that might mean accepting that the most frightening thing about Lake Iliamna is not what is in it. But how confidently we assumed we knew what was not. The Greenland shark that Jeremy Wade caught for river monsters was estimated to be over 200 years old. Somewhere in the black water at the bottom of Lake Iliamna, there may be animals that have been making that journey from the ocean, following the salmon. Since before Alaska was a state, since before it was a territory, since before Europeans had mapped the coastline it sits on. They have been there the whole time. Patient, ancient, enormous. We were just not paying attention. The monster in Lake Eliamna is real. The Edna says so. The century of witnesses says so. The geography says so. And the silence of the people who should have been investigating this decades ago says it loudest of all. The only question that remains is not whether it exists. It is why it took us this long to admit we needed to find out. My name is Matthew. This is Reef Discovery. And until next time, do yourself a favor. Next time you are near deep cold water and it is very calm and something dark moves below the surface just at the edge of where you can see clearly, don't assume you know what it is.