When buying sunscreen make sure you read the label, not all of them are the same. Always choose sunscreen with broad-spectrum protection against both UVA and UVB radiation. UVB rays cause sunburn and UVA rays contribute to skin aging and both are harmful to your skin. Only products that are specifically tested are labelled ‘broad-spectrum’.
You need to make sure that the sunscreen is SPF 30+ or higher. The SPF number indicates the degree of protection that the sunscreen provides against UVB radiation. SPF 30+ filters out about 97% of UVB rays and SPF 50 about 98%. No sunscreen gives you 100% protection.
When swimming you need to use water resistant sunscreen. No sunscreens are completely waterproof and, therefore, you need to reapply it according to manufacturer’s instructions to maintain its effectiveness. Sunscreen also rubs off when you dry yourself with a towel so you will need to put it on again.