The mysterious creature is believed by some to be the mythical Cadborosaurus, a reptilian sea serpent named after Cadboro Bay, in nearby British Columbia, where sightings have been previously reported.
The footage was shot by Alaskan fisherman in 2009, and will make its world premiere on Hillstranded, a new Discovery Channel special that will air for the first time the night of July 19.
The program stars Andy Hillstrand, who, along with his brother Jonathan, became well-known as a cast member of the Discovery Show Deadliest Catch. The show will explore the legend of the Cadborosaurus along with airing the video footage.
Hillstrand believes he may have seen the creature himself, while filming Hillstranded in Alaska.
We saw a big, long white thing moving in the water, Hillstrand told Discovery News. We chased it for about 20 minutes.
Spray came out of its head, he went on. It was definitely not a shark. A giant eel may be possible, but eels don't have humps that all move in unison. I've never seen anything like it before.
Paul LeBlond, former head of the Department of Earth and Ocean Sciences at the University of British Columbia is another believer, saying that he feels the 2009 video adds to its authentication.
LeBlond has reason to be enthusiastic about the possibility of documented evidence - he is co-author of the book Cadborosaurus: Survivor from the Deep.
I am quite impressed with the video, he told Discovery News. Although it was shot under rainy circumstances in a bouncy ship, it's very genuine.
LeBlond likens the sea serpent to a plesiosaur, a carnivorous aquatic reptile believed to have gone extinct during the Cretaceous Period.
Others are more skeptical.
People are working off of sketchy lay observations, said Jim Covel, senior manager of guest experience at California's Monterey Bay Aquarium. We do, however, still find new species in the oceans, perhaps allowing some to entertain ideas like this, filling in the gaps with their imaginations. But it really underscores how more scientific exploration is needed.
Hillstranded almost went extinct itself: In 2010, Discovery sued Andy and Jonathan Hillstrand, claiming they bailed on the planned spinoff of the popular show. But the lawsuit was later dropped, perhaps as insurance that the Hillstrand brothers would return to Deadliest Catch.