On a recent Saturday, I grabbed my towel and headed to the beach for a brisk November swim. I had a full wetsuit on, borrowed from a friend, and only stayed in for a few strokes, but the experience took my breath away—in a good way. My body had never felt so invigorated and energized, the effects of which lingered for hours and contributed to a euphoric glow well-known to open-water enthusiasts. My next thought: Where can I buy a wetsuit? Because I want to do this again.