Great Bay is a location in The Legend of Zelda: Majora's Mask. Located in western Termina, it is a large coastal bay leading out into the ocean. The Zora race make their home here, and in the surrounding sea. Skull Kid has placed a curse on the bay, causing the waters to slowly heat up, killing much of the marine life and forcing many of the Zora to take refuge in Zora Hall. Link meets the Zora guitarist Mikau here and after hearing his plight receives the Zora Mask, letting him take on Mikau's form and abilities.
In Super Smash Bros. Melee for the GameCube, the Great Bay was a stage that took place on the Marine Research Laboratory. In the background the Moon from the video game could be seen almost crashing down on Termina, though The Four Giants manage to push it away just in time. Tingle can be seen hovering above the stage via his balloon, which can be popped. The turtle from the video game will occasionally act as a platform, though be sure to get off of it when it sinks back down into the water.
Points of Interest
Great Bay Temple - The area's sole dungeon, and the game's third. Dead ends can be found throughout the entire maze like level. The temple is often compared to the Water Temple of The Legend of Zelda: Ocarina of Time in that it is considered to be the game's hardest dungeon (another comparison is the fact that they are both based around water).
Marine Research Laboratory - Arguably the area's most recognizable landmark, this is the location where scientists specializing in Marine Biology go.
Zora Hall - The location where most of the Zora are found.