WMG / Stranded Deep

The game takes place in another dimension.

1. There are way too many shipwrecks. Every island has at least one, and they've happened recently enough that there is always usable equipment that the saltwater hasn't ruined. There's even a beached aircraft carrier.
2. There are no other ships, or planes, or any other sign of living humans. With as many wrecks as you find, you'd expect this to be a busy enough shipping lane that a boat would show up to rescue you soon enough, but you never see another soul.
3. There is no escape. The minute you try, you somehow crash into your own plane that ditched in the ocean to strand you here in the first place.
4. You can find the long-dead remains of other castaways on the islands.

Conclusion: You've ended up in a self-contained pocket dimension that doesn't show up on any map, and you're not the first.