Limit sunbathing to early morning and late afternoon. During these hours the sun is lower in the sky, which means its rays go through a thicker layer of atmosphere. This reduces the amount of UVA and UVB light hitting your skin per hour of exposure.
Before settling down for a sunbathing session, slather on a thick layer of high SPF sunblock. This should be at least SPF 30, and the label should show that it is good for both UVA and UVB rays. UVA and UVB are two segments of the ultra-violet light spectrum. SPF 30 implies that for every hour of protected exposure your skin should receive a dose of UV light equal to 2 minutes of unprotected exposure.
Each time you go swimming, when you come out of the water, repeat Step 2. Even if you don't go into the water, use your watch and reapply sunblock every two hours.
After you've been sunbathing for an hour or two, move to a shaded spot.
If the sun is getting close to overhead (higher angle than 45 degrees above the horizon) put on cotton pants, cotton shirt and wide-brimmed hat. These clothes will protect you from burning better than any sunblock lotion.
