New Super Mario Bros. U: Sparkling Waters-4 -- Urchin Shoals

This level is filled with Urchins. Making things challenging is the fact that some of the Urchins are on waterspouts. Take some donut lifts down to the level of the Urchins and hit the brick block for a Mini Mushroom. Run along the water for the first Star Coin, then keep running up a waterspout to a mini pipe overhead. This leads to the second Star Coin. Just run to get it. Return to the main level and go a short distance to reach the midpoint. There are a series of Urchins over waterspouts that are under a platform. Use the Koopa shell to clear the Urchins for a 1-up. When the waterspouts appear, run over them to the left for a pipe. This leads to an underwater area where three giant Urchins guard the third Star Coin. There are more waterspouts with Urchins, as well as Red Coins. Jump over the Urchins at the end to reach the flag. This opens the path to Sparkling Waters-5.