To the South is Woodfall in The Legend of Zelda: Majora's Mask, a swamp-like area filled with octorocks, monkeys, and dekus. Located here is a swamp Tourist Info Center and Kotake's Potion shop. At the Tourist Center, you can have a tour boat chartered for you to easily access other parts of the swamp. Kotake's Potion shop sells potions of course.
You can reach the Deku Palace on foot using Deku Link, or get a safe trip on the tour boat. Inside the Deku Palace is the Deku king and his subjects, along with a monkey heading towards an unfrotunate fate.
On the opposite side of the river is the Woodfall Temple. Until the boss of the temple is defeated, the waters of the Deku side of the swamp are poisonous.