What Are The Recurrent Clear Fluid Filled Blisters On My Toes?

hi my right big toe develops blisters and when I pop them a clear fluid discharges. I mostly wear thongs and walk in the sea water. I wear business shoes and socks during business hours. Sometimes the blisters are tiny clusters other times they are larger but all only on the big toe. What is causing them and what is the best way to get rid of them?