Shark Island

A small landmass on the Mobian Ocean on Planet Mobius. In the Adventures of Sonic the Hedgehog episode Blackbot the Pirate, Doctor Robotnik, Scratch and Grounder travelled back in time 300 years to obtain the Chaos Emerald of Invisibility, which was buried on Shark Island. After landing on Blackbeard's ship and roboticizing the pirate, Robotnik took command of the vessel and set sail for the island. The island was covered with dense forest and laden with all manner of booby traps (even though the island appeared to be uninhabited and whoever set them up is not explained), though Scratch and Grounder only managed to set off one.

Robotnik lost the Emerald of Invisibilty to Sonic, who threw it through the Time Warp and it miraculously landed back in its original time and location. Robotnik returned to Shark Island in the AoStH episode Prehistoric Sonic to re-acquire the Emerald of Invisibility and found it before Sonic could stop him. He then left Sonic and Tails trapped on the island by using the Chaos Emerald of Life to turn an empty treasure chest into a crab, which ate Sonic and locked him inside itself. Sonic and Tails escaped Shark Island after Tails freed Sonic from the crab-chest by asking a female crab to seduce the crab-chest.

After the defeat of the Supreme High Robotnik, The Chaos Emerald of Invisibility was returned to Shark Island by Sonic and Tails's multiple selves.