At what water temperature does a diver typically start to experience excessive heat loss and become chilled?

Divers typically start to experience excessive heat loss and become chilled at water temperatures below 72 degrees Fahrenheit. At this temperature, the body loses heat faster than it can be produced, leading to an increased risk of hypothermia, especially during prolonged exposure.

This is significant because various factors including the diver's physical condition, duration of the dive, water currents, and what exposure protection the diver is wearing can all influence how quickly one might lose heat. However, 72 degrees F is often considered the threshold for comfort and safety, with many divers opting to wear thermal protection such as wetsuits or drysuits in these conditions to retain warmth.

Warmer temperatures, such as 75 or 80 degrees, generally do not pose a significant risk of excessive heat loss for most divers, allowing for a more extended and enjoyable diving experience without the same level of concern for thermal regulation. Conversely, diving in water below 68 degrees F is typically associated with a high risk of rapid heat loss, necessitating protective gear and careful planning to ensure safety.