4 Exostosis (surfer’s ear) Cause: Your inner ear defends itself against cold water by building up layers of calcium in the ear canal. Prevention: Loosen your grip on the paddle, choose a stick with less feather and work on strengthening your forearm muscles off the water. 6 Sprained ankle Cause: Your ankle rolls to the outside over top of your foot after missing a step on a portage, stretching or tearing the ligaments on the outside of the ankle.