From the Super Mario Wiki
Great Bay is an area in the land of Termina. In The Legend of Zelda: Majora's Mask, Link went here to free one of the Four Giants who lived in the Great Bay Temple from evil monsters in order to stop the Moon from crashing into Termina and destroying the world. Great Bay also appeared as a stage in Super Smash Bros. Melee, set upon a pier in the ocean housing a laboratory. The Moon plot of Majora's Mask is referenced as the Moon is shown getting bigger in the background until it almost crashes into the earth. The Four Giants then push the Moon back to its normal orbit. The music in the Great Bay stage is from the original Legend of Zelda, while the alternate track, Saria's Song, is from The Legend of Zelda: Ocarina of Time.
Great Bay is surrounded by water, which characters fall through to doom instead of swimming. There are two platforms next to the main pier, and one of them floats and sinks slightly when stood on. The ancient Turtle floats by the pier, and its shell can be used as a platform.. Every once in a while the turtle will go underwater, taking any players who happen to be on it with it. Tingle appears on the pier, floating on a small balloon that can be stood on. The balloon can be popped to send Tingle back to the ground, but it causes 1% of damage do the person who popped it. Tingle will quickly make another balloon again. If Tingle falls in the water, he will respawn on the pier after a few minutes.