Thermocline (temperature layer)

A thermocline is a sudden layer where water temperature drops quickly. You feel this as a cold wall while descending. In places like Anilao, you might swim through 28°C water before hitting a 22°C layer. This change happens because warmer surface water sits on top of colder, denser layers below. These shifts affect your buoyancy since warm water is less dense than cold water. I noticed my BCD required more air after crossing a sharp thermocline in Komodo in 2019. Always check your computer for temperature spikes. Do not panic if you feel a sudden chill. It is just physics at work. Carry a thicker wetsuit if you plan to dive deep in seasonal waters.