Consumer Reports tests sunscreens to find which offer the best protection.
Consumer Reports tested ten. Most promise to guard against both UVA and UVB rays.
Testers applied sunscreen to people's skin at an independent lab.
After waiting at least 15 minutes, they exposed the skin to UVB radiation, or UVA.
All the sunscreens offered good to excellent UVB protection. That's known as the SPF.
"The SPF or sun protection factor tells you how much sun you can handle before burning, compared to wearing no sunscreen at all. We recommend an SPF of at least 30," said Consumer Reports Jamie Kopf Hirsh.
But after sitting in water, nearly all the sunscreens lost a little UVB protection.
"You want to remember to reapply sunscreen after you swim or work up a sweat-and as a general rule every two hours," said Kopf Hirsh.
When it came to UVA rays, tests showed one of the lotions was just fair. It's Banana Boat Kids' Tear Free, with an SPF of 50.
But another lotion also marketed for kids did well-Coppertone's Water Babies. And adults can use it too.
If you prefer spray, save money by getting Target's Up and Up Sport Sunscreen Continuous Spray with an SPF of 30. It was the least expensive sunscreen tested.
And whether you spray sunscreen on or rub it in, use a generous amount.
A word about skin cancer-Consumer Reports says don't rely on sunscreen alone for protection.
Take other precautions like wearing a hat and tightly woven clothing.
And remember the best protection: Stay in the shade during the hottest part of the day.