Chuuk Barrier Reef

Chuuk, a state of the Federated States of Micronesia, has a spectacular barrier reef extending outwards from its volcanic islands. Here is a segment of it; the ocean falls off quickly to the top right.

The reef is huge, enclosing a lagoon of over 2000 sq km. It was Japan's last naval stronghold in WWII, and is a graveyard that was filled with numerous Japanese ships and airplanes when the US captured it in February 1944.