The first part of the level is a large basin that is
entirely water, although in the remake there are
some bricks above the surface to stand on.
Under the water is a giant whirlpool and some
chests. After that, there is a passage leading
to the Sub Room.
The second part of the level is a large area that (at first) will contain a large submarine and several platforms.
The ceiling contains climbable platforms that contain the Red Coins of the level.
There are also some structures underwater, one of which contains a sta for the level.
Star 1 - Board Bowser's Sub Edit
Mario must make his way into the second part of the level, and board the large submarine in the room. Then, collect the star.
Star 2 - Chests in the Current Edit
Mario must make his way to the bottom of the basin, which has four chests that must be opened in a certain order. The order is, the Chet's farthest from the passage, the chest closest to the passage, the chest after that, and the chest closest to the whirlpool.
Star 3 - Pole Jumping for Red Coins Edit
Mario must collect all eight red coins found in the Sub Room.
Star 4 - Through the Jet Stream Edit
Mario must go to the sub room and grab the Metal Cap in there. He must then collect a star near a jet stream in the water.
Star 5 - Into The Cage Edit
Star 6 - The Manta Ray's Reward Edit
Mario must find a Manta near the chests, and must fly through the rings the Manta makes.
Star 7 - Koopa Surfin' Switch Star (DS) Edit
Wario must make his way where some black blocks are. Smashing them will give him a Koopa Shell. Breaking another block will reveal the Switch Star button, which will then generate the star. Wario must make his way to the star by riding the Koopa Shell.