Jellyfish Lake, Palau
This magical lake is full of marine animals and it’s located in the Palau Islands. All the jellyfish that live there are quite small, so their stingers are not dangerous for humans (normal jellyfish can cause serious stings). Since jellyfish are beautiful animals, the experience is unforgettable: you can swim with them and even touch them. The protocol to get in is strict though. You have to make sure you have no sand on you whatsoever and you cannot use sunscreen or any other substance that could pose a threat to the delicate balance of their ecosystem.
All these security measures are to be followed by everyone in order to preserve the habitat of these jellyfish and prevent them from disappearing from the lake. In 2007 the lake was reported to host up to 5 million jellyfish, but by 2018 that number had significantly decreased to just 630,000 golden jellyfish living in this UNESCO protected site.
https://en.m.wikipedia.org/wiki/Ca%C3%B1o_Cristales