New Super Mario Bros. U: Superstar Road-3 -- Swim for Your Life!

This level is not as fast-paced as Superstar Road-2, but it is still hectic. It's an underwater level with a giant, man-eating Cheep-Cheep chasing you the entire way. You'll want a Fire Flower here to keep it in check. The giant Cheep-Cheep will knock Urchins and all other enemies out of its path, and try to eat Mario. You'll want to keep firing a few fireballs to the left every few seconds to keep it away. The first Star Coin is guarded by Urchins. Either use fireballs, or lure the giant Cheep-Cheep into knocking them out of the way for you. Same goes for the wall of Urchins to the right. Past the wall of Urchins is a set of currents. Some Urchins are floating in the currents, as well as the second Star Coin. It will hang out near the ceiling or the floor, out of reach, then move periodically to the other side. Be in the currents when it moves to collect it. Past it is a wall of Cheep-Cheep and an item block between two pipes. Homing blue Cheep-Cheep will appear and swim behind you, so don't stop swimming. Now you can leave the giant Cheep-Cheep alone for a while, as it will get rid of the blue Cheep-Cheep for you. At the end, feel free to use fireballs to get rid of it. The third Star Coin is just below the pipe at the end, guarded by Urchins. Use fireballs to get rid of them or have the giant Cheep-Cheep do that for you. Once you have the Star Coin, swim through the pipe and go to the flagpole.