When you go swimming in the ocean with only a bathing suit on. Then the ocean water evaporates leaving your balls laden with salt. The friction generated when the salty ball(s) rub against your leg causes painful burning afterwards.
Guy 1: Dude why aren't you keeping with the pack we have only been walking on the beach for 2 minutes.
Guy 2: I went swimming earlier in the ocean and now I got vicious SBS (Salty Ball Syndrome).