Jellyfish Lake

Jellyfish Lake (Ongeim'l Tketau in Palauan) is one of the world's most extraordinary natural wonders — a marine lake in the limestone heart of Eil Malk Island, Palau, inhabited by millions of golden jellyfish (Mastigias papua etpisoni) that migrate daily across the lake following the sun. The lake is a snorkeling-only site (scuba diving is prohibited to protect the ecosystem), offering a surreal experience that is less like ocean swimming and more like floating through a living galaxy of translucent golden creatures. The lake is accessed via a short jungle trail from the boat landing to the lake's edge, where snorkelers enter and swim to the central concentration of jellyfish, typically about 100 meters offshore at 1-5 meter depth. The golden jellyfish population evolved in isolation over 12,000 years after the lake was sealed from the ocean by sea-level changes, losing their stinging ability (almost entirely — sensitive-skinned visitors may feel very mild effects). A second species, the moon jellyfish, inhabits the deeper parts of the lake. The jellyfish migration follows the sun daily — they swim eastward in the morning to bask on the eastern shore, drift centrally during midday, then swim westward in afternoon. The behavior is driven by symbiotic algae in their tissues that photosynthesize, feeding the jellyfish. Below 15 meters the lake is anoxic and contains toxic hydrogen sulfide — scuba diving is prohibited for this reason as well as conservation. Jellyfish Lake is pure snorkeling — no fins allowed (to protect the jellyfish), no sunscreen (to protect the water chemistry), and strict numerical limits on daily visitors enforced by the Palau Koror State government. Reached by day boat from Koror (45 minutes), with a $100 permit required on top of dive package fees. Water temperature 29-31°C. The lake occasionally experiences population crashes (notably 1999-2012) linked to El Niño events, but has rebounded strongly.