Wednesday, February 3, 2016

Jellyfish Lake: Swim Safely With Swarms of Harmless Jellyfish

Jellyfish Lake
Jellyfish Lake
Photo by Onyo
Jellyfish Lake is one of five unique lakes that can be found on Mecherchar Island in Palau, Micronesia. It is known as Ongeim’l Tketau by the locals. What is so unique about these lakes is that they are the only places on Earth where a person can swim with millions of jellyfish without fear of being killed. Jellyfish Lake is the only one of these lakes that is open to the public for swimming and snorkeling. Therefore, it is the most famous.

Jellyfish Lake is a saltwater lake that was once connected to the Pacific Ocean. The lake is roughly 98.4 feet deep and covers an area of 12 acres. When the separation between the lake and the ocean occurred, some species of sea creatures became trapped in the lake. One of these species was the ancestor of the Mastigius jellyfish that now occupy Jellyfish Lake.

Jellyfish Lake is filled with more than 10,000 jellyfish of the Mastigius species. These jellyfish are also sometimes known as Darwin’s jellyfish. Since these jellyfish have become cut off from the ocean, they have adapted to life with very few predators. Over time, their nemastocysts or “stinging cells” have become smaller and smaller. They have been minimized to the point that these jellyfish are virtually harmless to humans. This is absolutely unheard of anywhere else on Earth.

Visitors to Jellyfish Lake not only get to have the otherworldly experience of swimming with jellyfish, but they get to witness an odd jellyfish migration of sorts. Each day, during the early morning hours, all of the jellyfish move toward the eastern side of the lake. At midmorning they all swim to the western side of the lake. This is done to optimize the amount of sunlight available to their main food source (algae). At night, they all move closer to the floor of the lake, where there is a significant build up of hydrogen sulfide (also beneficial to the algae).

Jellyfish Lake is a one-of-a-kind place and the Palau authorities are determined to keep it that way. Visitors are asked to be very careful not to litter. They are also asked to stick to snorkeling and swimming. SCUBA gear can affect the delicate balance of the lake. It is important that this lake and its counterparts be preserved for future generations.


Jellyfish Lake, retrieved 2/5/10,

Palau Jellyfish Lake, retrieved 2/5/10,

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