Located on an uninhabited rock island off the coast of Koror in Palau, Jellyfish Lake is one of 70 saltwater lakes on this South Pacific archipelago that were once connected to the ocean, but are now cut off.
The isolated lakes became the perfect setting for a jellyfish explosion, which some speculate were trapped in the lake 12,000 years ago after a rise in sea levels post-Ice Age. Feeding on quick-growing algae and with no predators to keep them in check, the jellyfish now completely pack the small lake. Though the jellyfish do have stingers, they are too small to be felt by humans.
Swimming in the lake is safe and permitted, but scuba diving is not as it may disturb the ecosystem. Also, you will want to stay away from the dangerous layer of hydrogen sulfide that hovers between 15 and 20 meters deep.
During the day, the jellyfish migrate from one side of the lake to the other to follow the path of the sun, which feeds the algae they survive on.