New Super Mario Bros. 2: 3- Fort

The level starts out on a platform just above the water, where a Fishbone swims around. Hop in the water and go left. If the Fishbone sees you, it will swim towards you until it runs into you or something else, which will cause it to break apart. Drop slightly down the gap and swim left to an new room with moving stones. The first Star Coin is to the left over the item blocks. Go back and through the green pipe on the right. The level becomes a vertical automatic sidescroller, with you swimming to avoid Fishbones and moving stones. The second Star Coin is on the right, past two sets of stones with spikes. The stones blocking your way will move up and out of your way. There are spiked pillars in this area. The midpoint is blocked off, so you'll be safe for a while. Get a powerup and Gold Block while you're there. As you swim up, you'll see a Red Coin Ring between pipes with currents. Go through the green one for the third Star Coin. Carefully swim up, avoiding Fishbones and spiked pillars. Go through the green pipe at the top. There are a couple of item blocks to the left of the boss door. There are four Reznor this time. Just hit the blocks below them. If the floor starts disappearing before you can get them all, hop on one of the blocks one was standing on. Once you defeat them all, Wendy drops in, then takes Peach to the castle.
If you happen to be Mini Mario, there's a mini pipe below the midpoint to the right. The level automatically scrolls up past moving stones and spiked pillars. At one point, you'll stop between stones. Stones will come in from the sides, first the bottom, then top, then center, then both the top and bottom, then the center. Avoid being crushed. The stones will then close in from the bottom, but you'll eventually be able to swim up. Don't swim up too quickly, as there are stones, spike pillars, and a Fishbone directly above. Stay below the Fishbone as you won't be able to swim up before the pillars and stones close in on you. The brick blocks to the left contain 2 1-ups. The red pipe to the right opens up the path to the cannon.

Coin Total: 19,507