Obviously, the face can get sunburned if you're out swimming in a pool or in the ocean. The water surface acts like one of those sun reflectors used by office workers in the park to get a good deep scorch on a short lunch break.

But water isn't as reflective a surface as, say, beach sand, which reflects 37 percent of the sunlight cast upon it. Water reflects only 9 percent of sunlight, and only 5 percent of the portion of sunlight most responsible for the skin damage -- ultraviolet B.

That means that the rest of your body, the part submerged in water, is being exposed to 95 percent of the damaging rays of the sun. Ultraviolet rays go right through the water, so if you're standing in the lake up to your neck, it's as though you're standing out in the open as far as sunburn potential is concerned. What's more, many sunscreens wash off, making it actually more dangerous to be submerged than to be out in the open with a good sunscreen.

One way around this problem, short of staying out of the water and in the shade when the sun is strongest (between 11 a.m. and 3 p.m. daylight-saving time), is to wear a truly waterproof sunscreen. Most sunscreens eventually wash off. Even "waterproof" sunscreens lose their sunburn protection after 80 minutes in the water, and "water resistant" ones after 40 minutes.

And swimming in a T-shirt doesn't help; the sun's rays pass right through cotton when it gets wet.

Two products introduced this summer may guard people from sun damage even

when they're wet. Chattem Inc. executives say their new product, Bullfrog Amphibious Sunblock, maintains a sun protection factor of 18 for six hours, even after swimming or sweating.

And Manhattan Ice Inc. has modernized the white zinc oxide cream that lifeguards use for total sun protection and turned it into a day-glow colored product, Le Zink, aimed at the teen-age beach crowd. Le Zink comes in pink, red, yellow, green, orange and blue, and each $5 pot, says the company, "covers approximately 400 noses, 500 eyelids, 50 broad shoulders, or 50 pairs of size-8 feet."

Another approach might be to provide protection from the inside out. At the University of Arizona, scientists are about to begin human testing of a synthetic hormone to give people the look -- and the protection -- of a tan without exposure to ultraviolet light. The hormone, to be taken either as a pill or a lotion, stimulates the production of melanocytes, cells that produce the pigment that darken the skin.

"This means you're tan, and protected somewhat from the damaging effects of ultraviolet light, without ever going out in the sun," says Victor Hruby, the chemist who discovered the hormone while looking for a diagnostic test for melanoma, a form of skin cancer linked to sun exposure. "I think people would still need sunscreen to protect themselves, but there's no doubt in my mind that the drug can reduce the incidence of skin cancer."