From the Super Mario Wiki
Super Mario series
Super Mario Bros. 3
In this game, Boss Bass swim on the surface of the water trying to leap out and eat Mario if he gets too close. It does not matter if Mario is small or big, or has any power-up equipped, Boss Bass will defeat Mario instantly in one gulp even if he was Statue Mario. In both of the stages he appears in, the water level rises and sinks, making Mario an easy target. Throwing blocks, shells, hammers, and fireballs can defeat him as well as tail attacks and Super Star, but he'll eventually come back. However, in Super Mario Advance 4, if the player has set on the e-reader card that will make enemies hit by fireballs turn into coins, and the player successfully hits Boss Bass with a fireball and collects the coin, Boss Bass will not return for the rest of the level.
Super Mario 64 / Super Mario 64 DS
In Super Mario 64, Boss Bass (known here as Bubba) appear in two places on the Tiny-Huge Island course. Like Cheep Cheep, they have been redesigned with visible orange and yellow scales, and they also wear sunglasses. They aim in on the player character with their mouth wide open, attempting to eat them. If a character is eaten, that character will lose a life, regardless of their current health. In Super Mario 64 DS, their design was reverted to their original one, and the closest one can be defeated with a nearby Super Mushroom.
In Mario Golf for the Nintendo 64, either a Boss Bass in its Super Mario 64 design or a Blurp from Yoshi's Story will jump out of the water if the ball lands in it. They are also much smaller in this game.
Mario Kart DS
Yoshi's Island DS
Boss Bass are also found in Yoshi's Island DS. They patrol their own little section of water, and periodically leap out in an attempt to swallow Yoshi (and even the baby) whole. Yoshi will not be eaten if they are at "jumping" process but will be if at "descending" state. There is also a mid-boss in World 3, Bessie Bass.
Mario Party DS
In Cheep Chump, a Boss Bass appears as one of the Cheep Cheeps in the water. Like all the others, it can suck Mario and his friends up and spit them out.
The Adventures of Super Mario Bros. 3
Boss Bass made appearances in The Adventures of Super Mario Bros. 3, where they usually chased after the good guys. Since they were never referred to by name, it is possible that they were intended to be Big Berthas, but they are not seen with Baby Cheeps.
Characteristics and traits
Boss Bass apparently eat Cheep Cheeps, despite being a relative of theirs. They also have trouble distinguishing them from something else, as proven in Super Paper Mario when a Shayde said that he fell into the ocean once, but luckily could swim as well as a Cheep Cheep. Unfortunately, a Boss Bass thought that since he swam like a Cheep Cheep, he was a Cheep Cheep so the huge fish ate him.
Names in other languages