Mushroom Sea

The Mushroom Sea is a large body of water that is located in Dark Land next to Castle Koopa. It was only ever seen on The Adventures of Super Mario Bros. 3.

The Mushroom Sea was featured prominently in the episode "Reptiles in the Rose Garden". At first, Bowser had transported the White House (along with the President) to Dark Land so that Kootie Pie Koopa could rule the United States for her sweet sixteenth birthday. However, merely abducting the President wasn't enough, so Bowser vowed to send him where he'd never get rescued: the bottom of the Mushroom Sea.

Using his Levitation Beam, Bowser lifted the White House off of the ground and sent it over the Mushroom Sea, where he released it, letting it sink to the bottom. As the President was too busy talking on the phone to notice what had happened to his home, his wife feared for their lives, but there was nothing that she could do at this point.

Fortunately, Mario donned a Frog Suit and dove into the Mushroom Sea, dodging the Blooper Nanny, Baby Bloopers and the Jelectro that chased after him. Eventually, Mario made it to the White House and was greeted by a shocked Mrs. President. However, Mario quickly assembled a pump out of pipes to flush the water out of the White House, and raised it to the surface.

Later, after Mario and Luigi had taken control of the Doomship from the Sledge Bros., Mario used the Levitation Beam to lift the White House out of the Mushroom Sea, and warped it back to Washington, D.C..

Although it wasn't mentioned by name, the Mushroom Sea can been seen in two other episodes of The Adventures of Super Mario Bros. 3. In "Mind Your Mummy Mommy, Mario", Luigi, Princess Toadstool and Toad escaped from Castle Koopa on their Steam-Powered Mummy Sled, and used it to ride across the Mushroom Sea.

In "Never Koop a Koopa", Luigi and Toad wait behind in a boat on the Mushroom Sea, while Mario and Princess Toadstool enter Castle Koopa. When Mario and the Princess don't return, Luigi and Toad dive into the Mushroom Sea, and enter the castle through a drainpipe.

Trivia

 * In The Great Mission to Save Princess Peach, Bowser's Castle was surrounded by a much larger ocean and the The Super Mario Brothers Super Show! episode "Mario and Joliet" depicted a fortress of King Koopa's as having a small, Trouter-filled moat around it, although Bowser's Castle has never had any kind of body of water associated with it outside of these appearances.