Yes, you can clean your boat with bleach. In fact, bleach is often used as a cleaning agent for boats because it effectively kills mold and mildew. However, you should be aware that bleach can also damage the gel coat on your boat. The Gelcoat is a clear coating that protects the underlying fiberglass from UV damage and makes the boat's surface smooth and shiny. If you use bleach to clean your boat, rinse it off thoroughly afterward to prevent damage to the gel coat. You may also consider using a milder cleaning agent such as vinegar or soap.