Boss Bass

A Boss Bass is a huge Cheep Cheep first found in Super Mario Bros. 3. He has a counterpart called Big Bertha.

Super Mario Bros. 3
In this game, Boss Basses 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 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 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.

New Super Mario Bros.
The Cheep Chomp from New Super Mario Bros. has similar qualities to the Boss Basses, but to Big Berthas as well, as they live underwater and not seen on the surface. Another enemy in New Super Mario Bros., Spike Basses, patrol the surface of water levels, similar to the Boss Bass. However, Spike Basses will not try to eat Mario.

Mario Kart DS
A Boss Bass makes a small cameo in Mario Kart DS, where he jumps out of the water and over the course in Banshee Boardwalk. Boss Bass replaces the Cheep Cheep from the original Mario Kart 64 version.

Yoshi's Island DS
Boss Basses 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. There is also a mid-boss known as Bessie Bass.

Mario Party DS
In Cheep Chump, a Boss Bass (or possibly a Big Bertha) 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.

Characteristics and Traits
Boss Basses 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.

Trivia

 * In Super Paper Mario, the two Shaydes talking in the Underwhere chat about how they died. One story involves the left Shayde becoming a "Boss Bass Snack."
 * Boss Basses are similar in both appearance and behavior to the Big Red Blurps from Yoshi's Story.