To understand the Dirty Beach Mud Run, take a look at the water stations that pepper its 5k course. Yes, they serve water, but they also serve beer and shots to athletes 21 and older. The race, in other words, is more than an athletic challenge—it's also part beach party where costumes are encouraged, unfolding on Mexico's aptly named Sandy Beach.

The physical challenge element is not to be trifled with, though. Participants not only run 5k, but must conquer 15 obstacles and a couple surprises along the way. These include climbing hills of tires and sand, slithering through tunnels, and myriad mud challenges. It's all worth it, though. At the finish line, the race turns into a huge, waterfront afterparty, with more mud-covered denizens than a fashion show for pigs.