From Zelda Legends Wiki
Quartet of islands at G6, most primarily the central island, on which stands a colossal dead tree. Inhabited by the living Deku Tree and his children, the Koroks. The Nintendo Gallery is located on a smaller island, and the Forbidden Woods on the second-largest.
Appears to be itself a giant tree, rising up from the sea. A few Babas and Octoroks inhabit the ground near the tree entrance, keeping people from wandering up a stream into the presence of the Deku Tree.
The water flowing from inside of Forest Haven has special purity which can be used to invigorate the Korok's saplings. However, the purity does have a time limit, and only the water collected from inside the tree walls is pure.
Upon first ariving at Forest Haven the Deku Tree seems to be having a Chu infestation. Once a handful are defeated in front of the tree, the place becomes serene and calming. A lilting wooden theme flowing across a bumbling brass theme gives the area a very distinct feel from previous Zelda Forests.