SSI Open Water Diver Practice Exam 2025 – Complete Study Resource

The primary factor that contributes to heat loss for divers is convection. Convection refers to the process by which heat is transferred from one material to another through the movement of fluids, such as water. When a diver is submerged in water, the body generates heat, but if the surrounding water is colder than the diver's body temperature, heat is continuously lost to the water. The moving water surrounding the diver, especially in currents or waves, increases the rate of heat loss because it replaces the warmer water that clings to the body with cooler water.

This means that as the diver remains in the water, and especially when the water is moving, they experience a significant decrease in body temperature, leading to potential thermal discomfort or danger from hypothermia if not properly insulated with a wet suit or drysuit. Understanding convection is crucial for divers to be aware of the need for proper thermal protection when diving in cooler conditions.