Bloat (the voice of Brad Garrett) is a Spiky Pufferfish. He has a temper and tends to argue with a lot with some of the other members of the fish tank gang and usually ends up blowing himself up. He is also Gill’s trusted lieutenant in running things in the tank.

Pufferfish are tube shaped fish (when not blown up) which get thinner toward their dorsal fin. They are generally peaceful but will become aggressive if it feels threatened, it will inflate to scare away the threat by inhaling water. If it is caught by another fish it will still inflate in the fish's mouth and will kill itself and the other fish.