The circumspect diving supervisor and diver should fully understand all conditions involved before planning or executing any work in hazardous temperature environments. Everyone assigned to a diving crew must understand and take seriously the dangers and exposure limits of the human body to adverse temperature conditions. Many misconceptions need to be resolved in order for a crew to understand the grave dangers involved in extreme temperature diving projects. Hot water conditions Divers working in temperatures above 88 degrees F. must be aware that they can be subject to hyperthermia as well as dehydration. When submerged, the human body's capacity to cool itself by evaporation is no longer possible and conduction becomes the main method of expelling heat.
Water is a very good conductor and directs heat away from the body.
A swimmer at rest can become chilled rapidly in a temperature which would be uncomfortably warm in moist air. However, when the temperature of the water approaches the human body temperature, the rate at which the body expels heat is greatly reduced. When you add a diving suit and a diver who is performing physical work, the chances of overheating becomes amplified exponentially. Up to about 91 degrees F. a diver can perform underwater if he learns to pace himself at the task at hand. The key to performing successful operations in this temperature range lies in limiting the diver's stay time based on his experience and physical conditioning.