A diver with a rapid pulse, hot dry skin, and no sweating is likely suffering from:

The symptoms of a rapid pulse, hot dry skin, and the absence of sweating indicate the presence of heat stroke. This condition is a severe form of heat illness that occurs when the body's temperature regulation fails, often as a result of prolonged exposure to high temperatures or strenuous activity in hot weather. In heat stroke, the body's ability to cool itself through sweating is impaired, leading to hyperthermia (elevated body temperature) and other serious symptoms.

Unlike heat exhaustion, which typically presents with symptoms such as profuse sweating, paleness, and weakness, heat stroke results in an inability to sweat, which explains the dry skin. The rapid pulse is the body's response to the extreme heat, as it tries to maintain adequate blood flow to vital organs. This is a medical emergency and requires immediate intervention, making it crucial for divers and others in hot environments to be aware of these signs and act promptly.

Other conditions listed, like hypothermia and sunburn, do not fit the symptom profile presented. Hypothermia relates to low body temperature, while sunburn is a skin condition caused by UV exposure, without the systemic symptoms that accompany heat stroke.