Jellyfish Lake in the Rock Islands, Palau

World-famous among divers, Jellyfish Lake on the Rock Islands in Palau is located on the uninhabited limestone island of Eil Malk. The jellyfish that populate it have no natural enemies and therefore no poisonous tentacles. Snorkellers can safely move through swarms of tens of thousands of the ghostly animals.

World-famous among divers, Jellyfish Lake on the Rock Islands in Palau is located on the uninhabited limestone island of Eil Malk. It was formed about 12,000 years ago when rising sea levels caused salt water to seep through the karst rock of the Rock Islands and collect in the basin of what is now Jellyfish Lake. Eil Malk is about a 45-minute boat ride from Koror.


The fascinating brackish water lake is 420 by 200 metres, up to 30 metres deep and the only one of the 70 marine lakes on Palau that is open to the public. Its water level is on a par with the sea level; with a delay of about 1.5 hours, even the tides are visible. The lake is actually called Ongeim'l Tketau. Jellyfish Lake, it is called because of its unique inhabitants. In its salt water, which is also mixed with fresh water in the first 3 metres, countless jellyfish cavort. Divers who come across jellyfish usually give them a wide berth because their tentacles are poisonous and cause a terrible burning sensation on the skin, and some species can even kill.

Swimming with jellyfish?

Jellyfish Lake in the Rock Islands is probably the only place in the world where you can swim with jellyfish. It is home to the pale yellow Mastigias Medusae jellyfish, also known as the Golden Jellyfish, or simply Medusa, which grows up to 23 cm in size. Since the translucent water dwellers have virtually no natural enemies in their lake, which is secluded from the outside world, their tentacles are also non-toxic. Snorkellers therefore need have no fear and can get up close and personal with the ghostly creatures in the approximately 30°C warm water.

The jellyfish that populate Jellyfish Lake in the Rock Islands have no natural enemies and therefore no poisonous tentacles, Palau - © Ethan Daniels / Shutterstock
© Ethan Daniels / Shutterstock

Deeper diving with oxygen tanks is not allowed in Jellyfish Lake. Firstly, the rising oxygen bubbles can get caught in the umbrellas of the jellyfish and secondly, the water is permeated with sulphuric acid from a depth of about 15 metres, which can even be fatal for a diver. This is also the reason why the medusae never get below this depth. From about 15m, there is no more oxygen. Other animals in the lake do not get above the size of snails, sponges and crabs. Other medusa habitats are Clear Lake also on Eil Malk and Goby Lake and Big Jellyfish Lake on Koror.

Tip: The jellyfish are supported in their feeding by unicellular organisms that live on a certain type of algae. Algae need light to live and therefore most medusae are always found where the sun shines most intensively on the lake, from morning to evening they follow the daylight. In addition, the only enemies of the jellyfish - solid sea anemones - live in the shade.

According to estimates, about 30 million of these fascinating animals live in Jellyfish Lake. Swimming around among thousands of them in complete safety is an unforgettable experience that should not be missed if you are ever on Palau.

And so it sometimes happens that you run into holidaymakers in the rainforest of Eil Malk who are walking through the dense jungle armed with diving goggles, snorkels and fins. The path from the coast to Jellyfish Lake takes about 30 minutes over two steep hills through the jungle of the Rock Islands.

Related links:

More info about Jellyfish Lake and the Medusae on Wikipedia