When entering this stage, you can collect bananas if you follow the left/right wave.
After landing, proceed to the right. In the second pool of water, you will find a . Directly below the K is a secret tunnel that contains two banana tokens. It is slightly longer than taking the direct approach, but still helps. Once the chamber is flooded, you may backtrack for some additional bananas and tokens.
You can find a swordfish, and an if you follow the ground. Once you turn up and head to the left, you will have to leave the swordfish behind, but can get a 1-up balloon if you bring him to the sign. Break the halfway barrel.
At the top of the level, exercise caution when heading to the right. When the corridor narrows just before entering a large room, have the swordfish perform a thrust as far as possible. This will bring you to the DK coin.