Thermocline
Definition
A thermocline is a distinct layer in the water column where temperature changes rapidly with depth.
More on Thermocline
Thermoclines form when warm surface water overlays cooler, denser water at depth. Divers experience them as sudden temperature drops, often accompanied by a visible shimmer or distortion in the water. They impact dive comfort, visibility, and marine life distribution. Knowing the depth of a thermocline can help with planning wetsuit thickness or locating certain fish species. Some thermoclines are gradual; others are sharp and disorienting.
Frequently Asked Questions
Divers feel a sudden temperature drop and may see a shimmering visual distortion.
Not directly, but the temperature change can cause discomfort or distraction, especially if unprepared.
Sometimes—especially with strong gradients, it appears as a blurry or wavy visual layer.
They vary—often found between 10–30 meters (30–100 feet), but can occur shallower or deeper depending on conditions.
Yes. Some species prefer certain temperature layers and congregate just above or below thermoclines.