Ursula takes Ariel to the sea, but she is confronted by King Triton, who agrees to take Ariel's place and is turned into a polyp, leaving Ursula to take over the kingdom.
With this plan worked, Flounder no longer transforms into the monster he keeps turning into, thanks to the silverfish.
Being as how they spend nearly every moment together, Flounder also acts as Ariel's confidant.