Thanks for all the positive replies, although as some have already mentioned regarding it possibly being a maul, I'd like to highlight its features of it being too narrow of a groove to haft a handle around it considering its weight, the lack of other marks suggesting it was bound with animal hide/strips of bark or other means to hold said wooden handle in place and the apparent lack of impact fractures that would suggest it being a hammering tool of sorts. The fact that the natives relied heavily on fishing in this area makes the notion of it being a weight much more realistic.
Glad to have spurred some discussion, nonetheless. Will gladly post updates on it or any further finds.