Manta

The Manta in Super Mario 64's Dire, Dire Docks level swims in a circle around the whirlpool in the center of the entrance area. The Manta will leave a trail of shimmering rings as it swims around the whirlpool. If you can swim through five rings in a row you'll be rewarded with a star. Swim through a ring to get oxygen, but if you touch the sides of one you will have to start over. If you swim into a ring correctly a red number will appear. When you accomplish your goal, the star will be at the top of the whirlpool. Don't get too close to the whirlpool or it will suck you in, and keep your distance from the manta's tail, it can deal damage.