By Stephanie Stahl

PHILADELPHIA (CBS) —  In spite of all the talk about the importance of sunscreen, millions of people still get sunburns. Most are minor but doctors say getting too much sun around water can be especially dangerous.

“I know the sun burns, but I didn’t think that it would be this catastrophic to where I’d have huge blisters, couldn’t walk, swollen legs and just in pain,” Katelyn Shipley, who received second-degree burns after tanning in the sun, said.

Shipley says it’s a lesson she learned the hard way.

“I’m the typical girl who is like, ‘Oh I want to tan, so I’m not going to wear sunscreen,'” she said.

After floating on the water for hours, Shipley got what her doctor says are second-degree burns. She says it first started with some burning and swelling, then huge blisters.

Doctors say being in or near water intensifies the dangerous ultraviolet light from the sun.

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“Sun burns can occur on sunny days,” Dr. Amy Person said. “On cloudy days, it’s more common when you’re in the water because of reflection.”

A recent study found white females who get five or more blistering sunburns between the ages of 15 and 20 have an 80 percent are at an increased risk for melanoma, the most deadly form of skin cancer.

“Sunscreen may not be the cool thing or it might not help you tan, but it’ll help you in the long run in the day to day,” Shipley said. “I could barely get out of bed.”

Doctors recommend a broad spectrum sunscreen SPF of at least 30. Covering up is a good idea too.

“Next time I go floating, I don’t care; I’m wearing pants and long sleeve shirts,” Shipley said. “I’ll deal with it but I’m going to put on sun screen from now on.”