It’s all this extra UV exposure that makes skin protection a constant challenge for cruisers when out on the water. Fortunately, most companies that make specialty sailing, surfing, and outdoor-activity clothing offer clothes specifically designed to protect skin from UV radiation, which is a nice alternative to slathering on the sunscreen or just staying in the shade of the bimini all day. While sun-protective clothing is nothing new, more and more clothing is now labeled as such, and the textile industry has adopted a standard rating system called the ultraviolet protection factor. Similar to the sun protection factor on bottles of sunscreen, the UPF rating is based on how much protection the garment provides. Clothing with a UPF of 15 to 24, which permits roughly 6.7 to 4.2 percent of UV transmission, is rated as “good”; clothing with a rating of UPF 25 to 39, which allows 4.1 to 2.6 percent of UV rays through, is rated as “very good”; clothing with a rating of UPF 40 to 50, which only allows 2.5 percent or less of UV transmission, is rated as “excellent.” Fabric that allows less than 2 percent of UV rays through is simply rated as UPF 50+. By way of comparison, “a plain white T-shirt has a UPF of about 7, and if it gets wet, that falls to about 3,” says Keri Hynes, the clothing specialist at West Marine’s store in Fort Lauderdale, Florida.