When dealing with ultraviolet light, the risk of skin damage and skin cancer is always present if the proper protection isn't applied.
Tanning beds are more dangerous because it is an intense exposure to UV rays for you're trying to get a quicker tan than you would sun bathing.
If your friend still applies adequate water-proof sunscreen, somewhere between SPF 25-50 depending on how sensitive his/her skin is, to all exposed parts of the body including skin just covered by the hems of the clothes for they do shift. Apply the sunscreen every 3-4 hours if you plan to spend all day at the beach.
Then your friend should be just fine. In case, bring some Aloe Vera to help quickening any sun burn recovery and significantly reduce the chance of skin cancer. Apply Aloe Vera every 2-3 hours, at least 2-3 times a day until damage is gone.