It is important to protect your skin from the sun. Here is a list of tips to follow when sun exposure:

Avoid exposure between 12 p.m. and 4 p.m., because these are the hours richest in burning rays (UVB)
Do not exceed one hour of sunbathing per day.
Always protect yourself with a hat / cap, anti UV t-shirt, sunglasses, etc.
Wipe off after each swim, as the water droplets reflect the rays and promote sunburn.
Apply sunscreen before each exposure to the sun, renew the application every two hours and after each swim.