Bingowings said:

Star Wars aliens tend not to look like proper creatures.

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.

I disagree. Ackbar has webbed hands, and sounds like he breathes through gills or some other organ that draws his breath through a certain amount of moisture. So there are both visual and auditory clues there. As for Chewie, he is similar to a bear in his type of skin covering....this might suggest that there is a cold season on his planet, or that the nights (or days) get cold.

Gungans have no webbed appendages. Their stumpy, elephant-like feet would push very little water while treading. Their ears serve no purpose while swimming (that we're shown) and would probably only get in the way what with their floppiness. They aren't shown as having gills, etc, etc........there's just nothing about them that suggests anything about an aquatic origin. They were a VERY bad design for a creature who's primary habitat is underwater.