Palau Jellyfish - Mass (Thysanostoma thysanura). Jellyfish Lake, Palau. Millions of years ago, jellyfish were trapped in this lake in the hills of Palau after a submerged reef rose from the sea, creating a landlocked saltwater lake. The lake is now home to millions of jellyfish, they have adapted to the new conditions by losing their sting and they follow the sun which is necessary for then to synthesize their food.