The significance of Gulliver's third travel.

During the third voyage, the ship that Gulliver is traveling on is overtaken by pirates. After insulting the Captain of the pirate ship, Gulliver is set adrift. When he reaches an island, Gulliver falls into an exhausted sleep. Upon awakening, he realizes that what he initially thought was a large cloud hovering over the island was actually another island..... a floating island.