In a saltwater lake in Palau, an archipelago in Micronesia with over 500 islands, millions of Golden Jellyfish spend their day following the sun as it crosses the sky over Jellyfish Lake. Unlike other jellyfish species, which seem to bob and float without a care in the ocean’s currents, these jellyfish need the sun. Actually, it's the algae that lives symbiotically in their tissues that need sunlight to survive. So the jellyfish spend their days propelling themselves through the water to stay in the sun, only to return to the other side of the lake at nightfall, ready to begin again the next day. For this 5-star service, the algae provide their jellyfish hosts with large amounts of energy via photosynthesis.
Perhaps even more unusually, around the time the lake separated from the ocean, these jellyfish lost both their natural predators and their ability to sting. People from around the world swim, snorkel and dive amongst them without fear and say you can tap the top of the jellyfish gently as you swim by, as if you are "petting puppies". Ginger Zee, from ABC's Good Morning America, recently went snorkelling in Jellyfish Lake and described her experience as "floating through a living lava lamp".