Two-Eye Reef
Two-Eye Reef is a reef located at D7. It has an Overworld check, a lookout platform, a Big Octo, and a sunken treasure.
Checks
Destroy the Cannons and Gunboats
Original Item: Treasure Chart 13
Type: Eye Reef Chests
Destroy all the cannons and gunboats in the interior of the eye reef to spawn a chest. Then, run along the exterior of the eye reef until you get to a point where you can Leaf to the chest.
Lookout Platform
Original Item: Purple Rupee
Type: Lookout Platforms and Rafts
Climb up the lookout platform found south of the eye reef to find a chest surrounded by many Bokoblins and Kargarocs.
Big Octo Great Fairy
Original Item: Magic Meter Upgrade
Type: Big Octos and Gunboats
Defeat the four-eyed Big Octo found slightly southwest of the eye reef. Doing so will save a Great Fairy who will give you your reward.
Sunken Treasure
Original Item: Triforce Shard 8
Type: Sunken Treasure
Open the treasure chart for Two-Eye Reef and salvage up the treasure using the Grappling Hook. Without randomized charts, the chart for Two-Eye Reef is Triforce Chart 8.