Unfortunately, there is no better solution to removing tan other than preventing Sun exposure. Plus, wet skin absorbs more of ultraviolet radiation than dry skin. Also, the sun sunscreen gets washed off so you practically will need to re-apply the sunscreen at least 3 to 4 times in those two hours of your swimming. What you could do is try getting a body covering swim suit. Barrier protection works best in such cases. To decrease your tan you will need to go to a dermatologist. Prescription Medicines might be required for good results. Do not try to use random creams based on watching a t.v. ad or because a friend said so. It might harm the skin.