Cressie is the name given to a creature , most described as a large eel, that is said to inhabit
This article from 1999 gives the history of sightings and some eye witness testimony:
Sea creature may lead to new eel species
By E. Randall Floyd Sunday, March 21, 1999
Pierce Rideout had heard stories about "Cressie," a monster that supposedly inhabited
Skeptics scoff at such suggestions. They claim that public relations stunts and outright fraud account for 90 percent of the sightings, while the rest can be attributed to mistaken observations. One doubter insists that the frothing disturbances commonly associated with sightings are actually gas bubbles from decomposing pulpwood littering the lake bottom. But Royal Canadian Mounted Police divers have found compelling evidence that "monsters" inhabit
N.B. the deep sea larva turned out to be an egg sac from something else I believe not an eel larva.
In the summer of 2003 Cressie was seen again when a woman saw the creature swimming. Vivian Short of Roberts Arm rounded a corner while driving with a friend along the lake side. "I was just a screamin', 'We saw Cressie, we saw Cressie!' Excited, eh," she said. She described a snake-like creature with a fish-like head. "Well, I said to my friend, 'Oh my that's big. That could eat four or five people if they were swimming, like.'" Ada Rowsell, the town's clerk said she’d had several reports of sightings. People reported sighting some kind of a huge monster or sea serpent or some kind of a fish this year.
So another giant eel? Sounds a distinct possibility in this case, in view of what the divers found. I am not sure how deep the lake actually is but came across one report saying 30 0 feet. Eels tend to be bottom dwellers who only surface occasionally but also tend to swim side to side rather than undulate up and down as witnesses described. Of course with a giant eel it maybe has to change it’s way of moving because of it’s great size. Until one is caught we will not know.