Palau · Palau · Lagoon
Jellyfish Lake
Millions of golden jellyfish crossing a 12,000-year-old marine lake
Photo: Lukas from Munich, Germany · CC BY 2.0
Jellyfish Lake, or Ongeim'l Tketau, is a marine lake on Eil Malk island where millions of golden jellyfish migrate horizontally across the water every day. It is a snorkel rather than a dive: scuba equipment is not allowed, which keeps swimmers out of the anoxic layer below about 15 m. The upper layer is somewhat turbid, so the animals appear close in rather than as a distant cloud.
Also known as Ongeim'l Tketau.
Where it is and how deep
7.1611° N, 134.3761° EPublished position for this site.
The dive
The lake sits inland on Eil Malk, so getting there is a boat ride of roughly 45 minutes from Koror and then a short trail from the beach across to the water. You go in with mask, snorkel and fins; scuba equipment is not allowed. The upper, oxygenated layer is where everything happens, and it is somewhat turbid, with visibility limited to about 5 m, so the jellyfish come into view at close range.
Two species of scyphozoan jellyfish live in the lake: the golden jellyfish, Mastigias papua etpisoni, and a moon jellyfish, Aurelia sp. Millions of the golden jellyfish migrate horizontally across the lake every day, so where the concentration sits depends on when you arrive. The moon jellyfish have no organised migration and feed on copepods at night. Stay in the top few metres of water throughout: the lower half of the lake is the part to leave alone.
Background
The lake is around 12,000 years old, formed as sea level rose after the end of the last ice age; the estimate is based on its depth of about 30 m and a sediment thickness of at least 20 m. The golden jellyfish are not a fixed feature of it. Temperature increases during the 1998-1999 El Nino drove the population to zero, and it did not recover to pre-decline levels until May 2012.
Marine life and season
- Stingless jellyfish
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Prime | Prime | Prime | Prime | Good | Fair | Fair | Fair | Fair | Fair | Good | Prime |
Season follows Palau: Boats run every month; November to April has the best conditions, and June to December is typhoon season.
Know before you go
- Below about 15 m the lake is anoxic, with hydrogen sulfide rising to over 80 mg per litre at the bottom, and it can poison a diver through the skin; stay shallow.
- Visibility in the oxygenated layer is limited to about 5 m, so keep your group in sight rather than following the jellyfish across the lake.
Photos from Jellyfish Lake
cinz · CC BY 2.0
Shinji · CC BY 2.0
CT Snow · CC BY 2.0
Dive videos
Palau Jellyfish Lake! (Would you swim with a million jellyfish?) · BlueWorldTV on YouTube
Questions divers ask
Can you scuba dive in Jellyfish Lake?+
No. Scuba diving equipment is not allowed in the lake. The rule limits the depth anyone can reach, which keeps swimmers clear of the anoxic layer lower down, where hydrogen sulfide can be absorbed through the skin.
How old is Jellyfish Lake?+
Around 12,000 years. The estimate is based on the lake's depth of about 30 m, an estimated sediment thickness of at least 20 m, and the rise in sea level since the end of the last ice age.
Sources
- Jellyfish Lake — Wikipedia
Photo credits
- Aerial view of the marine lake ringed by dense jungle on Eil Malk island. by Lukas from Munich, Germany, CC BY 2.0, via Wikimedia Commons
- A single golden jellyfish pulses through green lake water. by cinz, CC BY 2.0, via Openverse
- Dozens of jellyfish drift together near the surface of the lake. by Shinji, CC BY 2.0, via Wikimedia Commons
- Side view of a golden jellyfish showing its clubbed oral arms. by CT Snow, CC BY 2.0, via Wikimedia Commons
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