Star Wars aliens tend not to look like proper creatures.
They tend to have a chimera aspect to them (Greedo is a rare exeption).
Ackbar has a cuttlefish face and he is implied to be amphibian too when there is no exterior evidence of him doing anything in the sea (his space ship isn't full of water for example).
There isn't anything in his native environment that points to why Chewie looks the way he does.
He is a Sasquatch in a spaceship and that's as far it goes.
Jar-Jar should have been Ackbar (he looks better and it would have served the narrative arc) but everything you can physically say about either amphibians could be said of both.