IN MY OPINION: The island of Kosrae is about a 45 min plane ride east of Pohnpei and on the "island hopper" route of Continental Micronesia. The island is small, the people of Kosrae are very hospitable, and because it's in the wet region of Micronesia, almost anything will grow there.
If you like reefs that have huge coral pinnacles and formations, and all of the associated reef fish, you'll really enjoy diving here. However, Kosrae doesn't have the wide diversity of diving that you'll find in Pohnpei, Yap, Palau, and even here on Guam.
For JUST a dive destination there are better choices. BUT for a combo land eco tours, total kick back vacation with a few days of diving, you'll absolutely love it here. This is a beautiful island.