The Seven-Star Isles are a collection of small but tall rock spires that peek from the Great Sea. A few Kargorocs guard the Seven-Star Isles.
Piece of Heart #11 (via Big Octo #1)
A 12-eyed Big Octo is found in this sector. Sail toward a flock of circling seagulls to find it. Use the Boomerang to target up to five of its large, yellow eyes at once. When all 12 eyes turn blue, the defeated Big Octo leaves behind a ring of light, which contains a chest. Use the Grappling Hook to haul up the chest, which contains Piece of Heart #11.
Rings of Light
Three rings of light around this island appear only under the light of a full moon. When you see them, use the Grappling Hook to pull up a Red Rupee in a chest from each one.
Treasure Chart #16 (via Sea Platforms)
Sail to the trio of Sea Platforms and climb the middle Sea Platform’s ladder. Defeat the first Wizzrobe that attacks you to reveal a chest there. Defeat the next Wizzrobe to reveal a chest on the north Sea Platform. Defeat the final two Wizzrobes to reveal a chest on the south Sea Platform. You can jump between the Sea Platforms to reach each chest. You find Treasure Chart #16 in one of the chests and minor rewards inside the other two.
Silver Rupee (via Treasure Chart #45)
Find and open Treasure Chart #45 (received from Mrs. Marie at Windfall Island [D2] after you give her 41 Joy Pendants) to pull a chest from the Great Sea near Seven-Star Isles. The chest contains a Silver Rupee.