Shark (Mario's Time Machine)
From the Super Mario Wiki
The Sharks are enemies that appear in the PC version of Mario's Time Machine. They appear while Mario is surfing and time-traveling to his next destination. They act as obstacles, with a single one appearing at a random point. When it appears, it starts swimming in circles before eventually speeding towards Mario. If Mario touches it, he loses all of his collected Mushrooms, unlike the Floating Mines that only take away one Mushroom upon contact.