The Alsworth and Hammersley Floatplane Sighting of the Iliamna Lake Monster, 1942

Iliamna Lake is Alaska's largest lake. It runs about 77 to 80 miles long and about 22 miles wide, and it is more than 1,000 feet deep. Benjamin Radford notes it holds about 15 times the volume of Loch Ness. Native oral histories already told of a dangerous creature in its waters.

1942. The fullest account gives the month as September. Babe Alsworth, a bush pilot and fishing guide, was flying a floatplane toward the village of Iliamna. The route crossed at Big Mountain and ran straight over the lake. With Alsworth was Bill Hammersley. Some accounts call Hammersley a fisherman, others a passenger. Matt Bille writes that Alsworth flew with three companions in all.

Near an unnamed island in the middle of the lake, something showed on the water. From the air, the shapes almost looked like boats. Alsworth took the plane down for a closer look, circling from one thousand feet down to three hundred feet.

They were not boats. They were animals. A school of them, roughly a dozen by some counts, several dozen by others. Alsworth described fishlike tails and elongated bodies, dull aluminum in colour. The heads were broad and blunt. Vertical tails slowly waved side to side. The first guess was ten feet long. But the animals were easily longer than the plane's floats. They looked like mini-submarines. Then they surged in the water and disappeared in a distinct wave disturbance.

In the fall of 1959, the millionaire monster hunter Tom Slick hired Alsworth specifically to find the monsters of Lake Iliamna. They searched that same spot more than one hundred times. Nothing was sighted.

In 1979 an Anchorage newspaper offered a reward for proof. Accounts disagree on the amount, $100,000 or $10,000. Nobody claimed it. The sightings kept coming, from the survey pilot Larry Rost in 1945 to nine witnesses west of Kokhanok in 2017.

The obvious suspect was the beluga whale. Hammersley rejected it. Belugas have white backs, tapering heads and horizontal tails, nothing like what the witnesses had seen. Jeremy Wade later ruled out belugas and pike as well.

White sturgeon became the favourite. Matt Bille says it appears to match most Iliamna accounts, and Jeremy Wade reached the same verdict on River Monsters in 2010. A sturgeon's tail is vertical and moves side to side, just as the 1942 description has it. In 2012 Bruce Wright of the Aleutian Pribilof Islands Association proposed the Pacific sleeper shark instead. "Certainly the size and the shape and the color seems to match," Wright said. Benjamin Radford pushed back. Sleeper sharks live in salt water. The lake is fresh.

The fullest telling comes from Loren Coleman and Jerome Clark's Cryptozoology A-Z (1999). No photograph, film or physical trace survives from that September flight. Yet every later hunt for Illie, up to the 2019 search with DNA testing and underwater video, traces back to two people in a floatplane and a school of shapes that looked like boats.