Palau is an archipelago of more than 500 islands, part of the Micronesia region in the western Pacific Ocean, well known for its scuba-diving and snorkeling sites. The lakes are on limestone islands fed with sea water thru cracks and fissures in the rocks. When the sea level rose following the end of the ice age, jellyfish became trapped in the lake. As there are no predators for the jellyfish to fend off, they lost their ability to sting through evolution. That's why you can safely swim with these creatures!