When I saw first photos and videos about the Jellyfish Lake, I thought it must be a movie scene. But it is not fake, the lake full of jellyfish is real and I am sure snorkeling in it could be weird but unforgettable!
General info about the Jellyfish Lake
The Jellyfish Lake (original name Ongeim’l Tketau) is located on the uninhabited Eil Malk Island off the coast of Koror in Palau. The Eil Malk Island is part of the Rock Islands, a group of small rocky islands between Koror and Peleliu.
There are more than 50 lakes on the Rocky Islands. These lakes are marine lakes, that means they are isolated bodies of seawater but connected to the ocean through tunnels and fissures. Each lake has an own characteristic, they are different in size, shape, temperature and marine life. The number and position of tunnels and the salinity affect what kind of marine species can live in the lakes.
There are two main types of the marine lakes : mixed and stratified. In the mixed lakes the salinity, amount of dissolved oxygen and temperature don't change with depth. In the stratified ones there is lack of oxygen in the deeper layers and high concentration of hydrogen sulfide.
The Jellyfish Lake is a 12.000 years old stratified lake, the lower, anoxic layer begins at 12-14 m (40-45 ft).
The upper layer is oxygenated, the stratification is persistent, mixing of the layers vertically does not occur due to some simple reasons:
- thanks to the tropical climate the seasonal temperature variation is small so there is no temperature inversion that could cause vertical mixing
- the big rocks and trees around the lake block the wind
- the primary water sources are close to the surface so there are currents only in the upper layers
The lake is connected to the sea via 3 tunnels. Through these 3 tunnels flows the tidal water in and out. About 2,5 % of the lake's water is exchanged during tidal flows, but as it is written above, the tidal water affects only the upper layer.
The anoxic layer contains high concentrations of phosphate and ammonia. These are dangerous, can be poisoned through the skin, so diving is not allowed, but the Jellyfish Lake is perfect for snorkeling!
The jellyfish and other inhabitant of the lake (few fish species and copepods) live in the upper oxygenated layer. The visibility is about 5 m (16 ft).
Interesting facts about the Jellyfish Lake's jellies
Two species of jellyfish can be found in the lake, the Golden Jellyfish and the Moon Jellyfish.
The Moon Jellies are less common. They are transparent "lazy jellies", don't move so much and spend the daylight hours feeding on plankton below the surface in the depth of 5 m (15 ft)
The Golden Jellyfish are more active, they are the main characters of the photos and videos made in the JellyFish Lake. The Golden Jellies spend their life migrating horizontally across the lake, they follow the sun across the sky. They begin mornings around 6 o'clock to swim toward the sunlight, from the western shore of the lake until they nearly reach the east shore and turn back in the afternoon.
But why are they following the sunlight? The question is good and the answer is simple: the golden jellyfish must stay out of the shadows to avoid capture them by the predatory sea anemone.
The size of these type of jellies is up to 15 cm (5,5 in). I know that most people are afraid of jellyfish, but don't worry, the jellies in the Jellyfish Lake are harmless, the myth tells that they have lost their stringers due to the isolation in a predator-free lake. The truth is that they strings are to small to be felt by humans. You may feel tingling if they contact with sensitive skin, but remember they are not dangerous!
Unfortunately the lake also suffers from climate changes and sea temperature warming. In 1998, when the warm water temperatures caused dramatic coral bleaching in the region, the golden jellyfish population had declined to zero. The reason was that symbiothic algeas live within the jellies and this algeas could not survive in the warmer water. Happily the population recovered when the water was cooler again in 2000 and nowadays the lake and the jellyfish are in good condition.
Useful tips and advice
The Jellyfish Lake is currently the only one marine lake on Palau which is open to tourists. Tour operators offer boat trips to the lake, it is a 45 minutes long ride from Koror. You need to pay a fee to acces the lake, I found that the pass is 100 USD and valid for 10 days, but check the actual prices if you plan your trip.
People with sensitive skin are suggested to wear protecting clothes. Do not dive deep, always swim in the upper layer.
The best is to wear fins during snorkeling to maintain greater control. Swim in a prone position slowly. Do not kick among the jellies with your fins or with your feet if you don't wear fins as you could rip or tear them.
Do not apply sunscreen before entering the lake and check that your equipment is clear.
If you follow these actions, you will help preserve the Jellyfish Lake and its magical jellies for the next generations as well!