The Sea of Time Islet is a small island located southeast of the Sea of Time and explorable in Golden Sun: The Lost Age. It is only inhabited by two old men and a tiny one-room hut, who serve to drop hints about how to defeat Poseidon. Also on the island is a turtle named Lonesome George, who desires a turtle friend of his own to break up the loneliness.
This is by no means an insignificant location from a gameplay perspective. If you give Lonesome George the Lil' Turtle "item" acquired from a dog at West Indra Islet, it will agree to ferry you to a nearby cave entrance in the water, which is the entrance to none other than the optional dungeon Islet Cave, where you can find the final possible Venus Djinni before the Poseidon boss battle. After acquiring the Teleport Lapis found at Mars Lighthouse, players can revisit this dungeon and explore the previously inaccessible second portion of it. Here, players will find the final Mercury Djinni and the Summon Tablet Catastrophe, guarded by the powerful optional boss, Sentinel. The second half of Islet Cave is also a great place for players to level grind, by repeatedly battling Wonder Birds found here.