Palace on the Sea

Located in eastern Hyrule, the Palace on the Sea is the fifth dungeon in Zelda II: The Adventure of Link, and is visited by Link during his quest to place one of the shards of the Magic Crystal to its lectern to gain access to the Great Palace, find the lost part of the Triforce and rouse Princess Zelda from her unnatural slumber.

Concept
As it is on an island completely separated from land, and there is no dock sufficient to launch his raft from, Link can only reach the Palace by walking on the water separating the tiny island from the mainland with the boots. This dungeon is notable for its trickery, not only because of its size, but also because it's the first one with a fake wall; a creature similar to the Wizzrobe debuts here, except Link can't repel its projectiles (fireburst, in this case).

Within the Palace walls, Link finds the Flute, useful to gain access to new areas with the help of music; the boss of the dungeon is the incredibly powerful Gooma.

Trivia

 * The path near the palace has a farther right turn where a Heart Container can be found.
 * Horsehead appears in the Japanese version of the game, while Gooma doesn't.