World 6-2 (New Super Mario Bros.)
From the Super Mario Wiki
This level has rising water similar to Mondo from Super Mario World. After the Red Warp Pipe, the player should see a ? Block with two coins above it. In between those coins are two invisible blocks, one containing a Beanstalk. Mario should climb it and press a P-Switch, jumping across some flying ? Blocks to get the first Star Coin. Soon after that, Mario should reach two tall cannons. One takes Mario to a bonus area with several flying ? Blocks containing a total of eight 1-Up Mushrooms and 120 coins, and the other is a Pipe Cannon that takes the player to the second Star Coin. Mario can get the last Star Coin by going past a few Spinies. When Mario goes through the yellow Warp Pipe, he will reach the Goal Pole.