Tuck away among the 7,107 islands in the Philippines, occasionally referred to as Luluyuan Lake by locals, its crystal blue waters it warm and unbelievably clear – a rare tranquil paradise for scuba divers and snorkelers. The lake is named Barracuda because the people found a giant barracuda skeleton in the lake. And as if the clear blue water contrasting with the dark limestone cliffs weren’t enough, this lake hides a secret that can’t be seen from the surface but can only be felt.

Starting from the surface of the lake until about 14m deep is the warm fresh water with a temperature of about 28 degrees Celsius. At depths below 14m to 35m, the water temperature increases from 28 degrees Celsius to 38 degrees Celsius, the water at the bottom also changes from clear green to tea brown, which occurs due to tannic acid from leaves falling into the lake.

Not only is the experience of the temperature change interesting, at 4 meters the water changes from fresh water to salt water. Here divers can see a heliocline (an area where water with different salinity contents mix). It looks almost like a long, thin, black-grey, horizontal tornado in the distance. Another heliocline can be seen at 14 meters.

The bottom of Barracuda Lake is a thick, soft, silky, silty sand. Divers often remove their fins in the shallows to play around in the sand and amongst the rocks and submerged tree-branches. This creates the effect that is often likened to what it might feel like to walk on the moon.

According to remotelands.com, atlasobscura.com, sanhodive.com