Hello,
From your symptoms it can be contact dermatitis or shingles. Shingles occurs in people who have had chickenpox and represents a reactivation of the dormant varicella-zoster virus. The first sign is usually a tingling feeling, itchiness, or stabbing pain on the skin. After a few days, a rash appears as a band or patch of raised dots on the side of the trunk or face. The rash develops into small, fluid-filled blisters which begin to dry out and crust over within several days. When the rash is at its peak, symptoms can range from mild itching to extreme and intense pain.
I suggest you to get it examined from a dermatologist. It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your dermatologist. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
No this does not sound like shingles. Shingles resembles chicken pox. My guess is that you've got a slight case of razor burn. The chemicals in the pool wouldn't help either as they are very drying to the skin and can make irritation worse.
Your best bet is to lube up in baby oil or a heavy lotion with vitamin E and/or aloe in it. Aloe will calm the rash, reduce redness and speed healing. If you must shave again in the future, be sure to exfoliate beforehand and apply a heavy lotion after you step out of the shower, while your skin is still damp. Try do this at least a few hours before you swim so your skin absorbs the moisture, and repeat again when you get out of the pool.