Boating Course
Boating Course is located at F7. It has an Overworld Check, a secret cave, a Blue Chuchu, and a sunken treasure.
Checks
Raft
Original Item: Boko Baba Seed
Type: Lookout Platforms and Rafts
Sail south of the island to find three rafts. The chest sits on the southern raft.
Cave
Original Item: Submarine Chart
Type: Puzzle Secret Caves, Combat Secret Caves
The entrance to this secret cave is on the north part of the island, which logically requires either Deku Leaf or Hookshot to access. Enter the cave and hit the three crystal switches with a ranged weapon to spawn the chest. Note that Miniblins will spawn endlessly within the cave.
Sunken Treasure
Original Item: Sea Hearts Chart
Type: Sunken Treasure
Open the treasure chart for Boating Course and salvage up the treasure using the Grappling Hook. Without randomized charts, the chart for Boating Course is Treasure Chart 32.