New Super Mario Bros.: 4-6

It's another purple water level. To help us cross the water, Dorrie returns. She will duck under platforms, so you may have to climb on them to avoid being pushed off into the water. There's a Red Coin ring near the platform with the first Star Coin. The Red Coins go under the platform as well as over, so you'll have to double back to get them all. You'll have to go over the platform with the Piranha Plants. The second Star Coin is past the P-Switch, which you must use to reach it. It will turn coins into brick blocks, giving you platforms. The ! Switch will allow you to go up a green pipe, where you'll find the third Star Coin in a coin formation after you slide down. There is a 1-up near the pipe. You'll end up near the pipe to the flagpole. The path to the castle will open up.