Underwater photographer Sarosh Jacob swims in Palau’s incredible Ongeim’l Tketau or Jellyfish Lake on Eil Malk island, reportedly the only marine lake in Palau that’s open to tourists when jellyfish populations are thriving. Only swimming and snorkeling is allowed.
Jellyfish Lake is connected to the ocean through fissures and tunnels in the limestone of an ancient Miocene reef. However the lake is sufficiently isolated and the conditions are different enough that the diversity of species in the lake is greatly reduced from the nearby lagoon. The golden jellyfish, Mastigias cf. papua etpisoni, and possibly other species in the lake have evolved to be substantially different from their close relatives living in the nearby lagoons.
Take one 3/4 full bucket of dirty water and leave it to sit somewhere sheltered out of reach for one week. If it’s left undisturbed, the sediment settles. What you get is your miniature version of a Meromictic Lake.
So what? You might ask, but I am going somewhere with this. So instead of having one three-quarter of a bucket, you now have a volume of approximately 94 million buckets and leave it to settle on an island in the central Western Pacific for 12,000 years or so. Here you have the famous Jellyfish Lake in Palau.
Next, watch Great Migrations: Jellyfish Lake.