What type of fish is flounder from the little mermaid.?

Presumably Flounder is a flounder, although he doesn't look like one. Flounder are bottom-feeding fish: they are flat fish that swim parallel to the ocean's bottom and surface (in other Words, they appear to lie flat on one side in the water). And they have two eyes on their top side (because the other side is perpetually facing the ocean floor).

They are creepy-looking fish (mostly because of those two eyes right next to each other on the top side). google "flounder fish pictures" and you'll see what I mean.

I would guess that the Disney animators made Flounder physiologically inaccurate because real Flounder are so creepy, and also for practical reasons: a flat fish that lies on one side is an impossible film character. In order to see the fish's "face," the camera perspective would have to keep switching to a top-side view (looking down from above the characters).

The rest of the time, the flounder would appear as a horizontal line floating in the water next to the other characters.