On an uninhabited island in Palau in the western Pacific Ocean, beneath the surface of a lake, there is a hidden world of seemingly alien life. Translucent amorphous creatures glide through the clear water, float lazily just beneath the surface of the lake, or drift along with the current. Thousands of years ago, these jellyfish were trapped in a natural basin on the island when the ocean receded. With time, they evolved into a new species that no longer stings. In Jellyfish Lake, the filmmaker Sarosh Jacob dives into the world of these wondrous creatures, and swims among them, recording their slow, mesmerising migrations.