Bubba

Bubbas are big pink or orange fish (usually wearing sunglasses) that will eat Mario if he gets too near them after a while. They look and act very similar to Boss Bass from Super Mario Bros. 3. Bubba appears to be a species of Blurp.

Super Mario 64
Two Bubbas appear in Tiny-Huge Island and they cannot be defeated similar to most aquatic enemies in Super Mario 64. If Mario is eaten, he will lose a life, regardless of his current health. In Super Mario 64 DS, they are replaced by Big Berthas.

Mario Party
Additionally, stepping on a Happening Space on Yoshi's Tropical Island, a gameboard in Mario Party, Bubba would eat Toad, switching Toad's and Bowser's position. Bubba lacks its trademark shades in this game, which makes it look more like its smaller counterpart.

Mario Golf
In Mario Golf for the Nintendo 64, either a Bubba or Blurp will jump out of the water if the ball lands in it. They are also much smaller in this game.

Trivia

 * The Cheep Cheeps from Super Mario Sunshine are often confused as Bubbas, but they do not wear sunglasses and are smaller in size.