While freediving you notice a thermocline without a doubt. Comfortably going down, but then suddenly UFF. A cold smack in the face.
A thermocline is an abrupt change in the temperature of water within a small depth. As warm water has a lower density than cold water, it creates a thin layer. That layer is called the thermocline, which separates the hot and cold water.
Most of the times in our areas the color of the water is different as well. Blue is warmer water. Green is colder water.
In general, fishes can´t cope with sudden temperature changes so they can´t really move between layers.
When spearfishing around thermoclines, it feels like you are hunting in the twilight zone…. Soooo interesting. Above you in the warm water there is different fish than underneath you in the cold water. And as a bonus, some fishes that like to hunt around the thermoclines.
This picture I took a couple of days ago. Some Horse-Eye Jacks that prefer the warm water. Underneath them the greener colder water.
Enjoy the thermoclines!