Chomp Shark

Chomp Sharks, also named Shark Chomps, or Giant Chomp-Chomps, are giant sized chainless Chain Chomps who constantly move forward while gnashing their jaws. Chomp Sharks primarily appear in the Yoshi franchise. They cannot be attacked, so Yoshis are forced to either run from them or avoid them entirely.

Super Mario World 2: Yoshi's Island
Shark Chomps (named Bow Wow on one occasion ) are introduced as one of the three varieties of "Chomps" in Super Mario World 2: Yoshi's Island, where they appear in Marching Milde's Fort and KEEP MOVING!!!! In the former level, the Shark Chomp appears right after a group of Incoming Chomps. These giant Chomps relentlessly chase after Yoshi, gnashing through anything in their way. Their appearances in certain levels make backtracking impossible, as they are almost invulnerable and will often eat anything on which Yoshi can land. Eventually, the Shark Chomp chases Yoshi to a platform it cannot eat and breaks its teeth, causing it to tear up in pain and fall off the screen.

Yoshi's Island DS
In Yoshi's Island DS, Shark Chomps act exactly as they do in Super Mario World 2: Yoshi's Island and even use the same sprite, though due to the lighter colors it seems to have been based off the Yoshi's Island: Super Mario Advance 3 sprite instead. One appears in Rompin', Stompin' Chomps.

Yoshi's New Island
In Yoshi's New Island, a Chomp Shark is the main feature of Chomp Shark Chase. Their teeth no longer crack, although, they still tear in pain.

Super Princess Peach
In Super Princess Peach, Shark Chomps are called Big Chain Chomps, a more accurate rendition of their Japanese name. They are found in Wavy Beach and Giddy Sky, specifically Wavy Beach 5-2, Wavy Beach 5-4, Giddy Sky 7-2 and Giddy Sky 7-8. Rather than eating terrain, Big Chain Chomps are usually found bouncing down hills provided with gaps in which the princess and her umbrella may hide. Some of them are also seen periodically falling down pits. They are noticeably smaller in this game, but still much larger than normal Chain Chomps. One is also seen in the background of the Wavy Beach world select screen, bouncing on the water surface, resembling Incoming Chomps' background sprites. According to the game's Glossary, Big Chain Chomp is "A giant Chain Chomp. Very dangerous!".

Super Mario World 2: Yoshi's Island

 * Official Nintendo Player's Guide: They eat everything in their path, including the path itself. Move fast or you'll be shark bait!

Trivia

 * The Chomps in Yoshi's Story, which also constantly move forward while perpetually chomping, are quite similar to and may have been based on the Shark Chomp. The Nintendo Player's Guide also takes note of their in-game size.