Hi Vie,
The sensations described are known as paresthesias and post-dive can indicate several conditions. Paresthesia is the second most common complaint in DCS, coming just after musculoskeletal pain. It can and often is the only symptom.
When these sensations occur on the skin, they can be the result of cutaneous DCS (aka "skin bends"), a condition that typically is benign and clears without treatment or residual, but can be an early warning signal with more serious features developing rapidly. Skin bends most commonly affect the torso and can range from a simple and very short-lasting pins-and-needles sensation to intensely itchy, mottled rashes.
However, given: (1) dive profiles which are not at all suggestive of DCS; (2) paresthesia of the rear thighs as the only symptom; (3) occurrence only after diving in relatively cool water; and, (4) sensations that last for extended periods, there are other potential causes to be ruled out.
High on the list would be a wetsuit (or other topside or u/w garment) or weight belt that is excessively snug in the hip, groin or thigh area and could result in compression of a superficial cutaneous nerve. Any likelihood this could be the case?
Is there any history of obesity, back problems or other medical condition?
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual and should not be construed as such.
Regards,
DocVikingo