What is a specific symptom of rapid ascent?

A specific symptom of rapid ascent is pressure imbalance. When a diver ascends too quickly, the change in pressure can lead to problems such as barotrauma, where the air spaces in the body (like the ears and lungs) fail to equalize with the external pressure. This pressure difference can cause discomfort and various symptoms, including pain in the ears or sinuses and potential injury to the lungs if the diver's air spaces are not allowed to expand at a safe rate.

Other symptoms associated with rapid ascent may manifest, but they are typically secondary to the pressure imbalance issue. For instance, barometric headache could occur due to the pressure changes, and skin irritations or muscle spasms might be symptoms of other conditions or stress factors rather than direct results of rapid ascent. However, the primary concern and a direct symptom related to rapid ascent is certainly the pressure imbalance, which poses immediate risks to the diver's health and safety.