One of the more unique experience that anyone can experience is the chance to snorkel in a lake full of jellyfish. There are several areas in the world which boast these incredible natural phenomena with the Jellyfish Lake of Palau being the most well known. What is not as well known is that the famous Palau Jellyfish Lake is but one of many that are found in the Palaun Islands. Indonesia is also home to many known jellyfish lakes and most likely others which have yet to be discovered.
The dominant jellyfish that are commonly found throughout the different lakes are usually a golden or pinkish coloured Mastigias species. Another type of jellyfish that is also present are Moon jellyfish of the Aurelia family. All of these lakes are also home to many varieties of gobies, cardinal fish, and anemones. The jellyfish themselves have been isolated from the ocean for so long that they have evolved a different life than their marine cousins. The golden jellies typically follow the sun throughout the day and avoid the shadows cast by mangrove trees. Both species of jellyfish still retain their stinging nematocysts but their power is much less than most marine jellyfish and only sting sensitive areas such as lips.
These jellyfish are very fragile to damage from swimmers, as well as climate change, with many occurances of die offs during El Nino years. In Indonesia, there are known lakes in Raja Ampat, Sulawesi, and Kalimantan (Borneo). Probably the most famous of these Indonesian lakes is Jellyfish Lake Kakaban in Kalimantan. The below video is from Kakaban and shows three different species of jellyfish: the Mastigias golden jellies, the Aurelia moon jellyfish, and the Cassiopea upside down jellyfish seen living on the bottom.
Learn more about Jellyfish Lakes at Wikipedia