Jellyfish Lake, Eil Malk Island, Palau, Pacific Ocean

Jellyfish Lake is around 12,000 years old. This age estimate is based on the depth of the lake (about 30 meters), an estimate of the thickness of the sediment (at least 20 meters) and the rising sea level since the end of the last ice age. About 12,000 years ago, the sea level had risen to the point that sea water began to fill the Jellyfish Lake basin.
Jellyfish species
Two species of scyphozoan jellyfish live in Jellyfish Lake, moon jellyfish (Aurelia sp.) and the golden jellyfish (Mastigias sp.).