Behold the Northern California coast: rugged, inspirational, and freakin' freezing. Where can you enjoy a shoreside swim without risking hypothermia? Try Bass Lake in Point Reyes National Seashore. It's a scenic 2.7-mile coastal hike up from the parking lot, and the water's warm (warmer than the Pacific, at least) and clean. A plunge into the Bass won't freeze your ass-but watch the posterior-poking nettles when you're changing in the bushes. We're also assuming you don't mind the occasional free-spirited skinny-dipper. Bonus: Pack a picnic and inflatable raft and make it your own backyard pool.

From the town of Bolinas, follow Mesa Rd. 4.6 miles past the Bird Observatory to the parking lot. Take the Coast Trail, and follow it 2.7 miles until you see Bass Lake on your left.