The problem is that the name and "History" for Willatuk was entirely made up for the one amateur film and that film's time has cone and gone Nonetheless there HAS BEEN historically a Seattle/Puget Sound version of "Cadborosaurus" for some time, There has been a reported "Lake Washington Sea Serpent" for some time, consensus of opinion is that both of them look like a Plesiosaur, and the "Traditions" of the (Made-up) Willatonka tribe can be charitably looked upon as an overly enthusiastic white man's retelling of some Sisiutl stories, or their local equivalent. So all of the "Willatuk" material is made up, BUT it is probably no more misleading than much of the hype told about any other local "Sea Serpent" up to including the Loch Ness Monster.
So if any of the locals takes to calling the Lake Washington Sea Serpent "Willatuk" instead, they can probably be forgiven, because the made-up Sea serpent is near enough to the real traditions to pass. I do not know if any of it continues to "Stick" locally though. The basic idea that most experts including Heuvelmans have is that ALL Sea-serpent reports off the West Coast of North America, from Alaska to California are local variations on "Cadborosaurus". There is also something to be said for that idea and at the same time also it is an idea that is very misleading. At one point, "Cadborosaurus" was a made-up journalistic category, it was not the name of any longstanding tradition, but it was a convenient label that could be used to cover the whole range of reports which were coming in.
Eberhard lists Lake Washington as one which has "Monster" reports but only indicates that sturgeon were the cause of sightings in that area. Other sources indicate ongoing sightings of a "Reptile"
Here is a photo of the Lake Washington monster Sturgeon. Lake Washington is only a little way in from the sea and could easily have more than one kind of "Monster" in it. This is interestingly enough from a Swedish newspaper that wonders if the monster in lake Stosjon could not also be a similar type of sturgeon.