The world knows a lot more about Bar Refaeli today than it did yesterday, including where her tiny tan line falls.

Sports Illustrated Swimsuit unveiled the 23-year-old Israeli, who has been romantically linked to Leonardo DiCaprio, as a first-time cover girl on Tuesday.

This gig, more than top fashion or entertainment magazines, can be career-altering as it puts a model’s face (not to mention, her fantastically toned body) in front of millions of eyeballs, appealing to both men and women, sports fans and fashionistas.

It’s the cover that matters most, says SI group editor Terry McDonell, but each model — 19 for this issue — gets an equal shot at the cover. Refaeli wears a string bikini by Missoni — and the strings on the bikini bottom are being tugged south.

“The cover has to reflect the athleticism and sexiness of the culture. This photo is modern, her hair and swimsuit look natural. You see her freckles. Her body is amazing and she looks intelligent,” McDonell said.

It’s also purposeful, he noted, that the models have healthy, sometimes curvy, figures. “A skinny waif won’t work here.”

McDonell, along with Swimsuit editor Diane Smith and SI creative director Steve Hoffman, sifted through 90,000 photos this year. In consumer testing, it’s inevitable that the raciest one is the favorite, but that’s not the one that lands on the front. “There are marketplace considerations,” McDonell explained. “I want to be at the front of the store, not the back.”

Refaeli told The Associated Press that she had the feeling that this particular shot of her in the water on Canouan Island in the Grenadines was her chance to be on the front.

“This is the one I felt the most comfortable with,” said Refaeli, who twice before was featured on the inside pages of the magazine. “You have the beach, blue water and a body. That’s it. I liked that the top of the suit was on.”

You can be sexy without revealing too much skin, said veteran supermodel Cheryl Tiegs, who first appeared on the Swimsuit issue cover in 1970 — and then again in 1975 and 1983.

That shot happened at the end of a full day shooting in Hawaii, and she was cold. Someone gave her long-sleeve top to warm her up and when the photographer asked her to take it off, Tiegs refused — and she wouldn’t take off her sunglasses either, she recalled. That photo, she said, really captured a moment, though.

“I remember walking by the newsstand and seeing I was on the cover and picking up a copy or two. That was the celebration then. … But I’m still signing covers for fans,” Tiegs said.

SI’s swimsuit issue began in 1964, when February marked the low point of the sports seasons. The NFL ended in December, there were no national televised hockey games and the NBA had only a half-dozen teams. After putting safe-driving tips and dog shows on the cover, SI decided to put an attractive female on the cover and call it a “skin-diving story,” recalls Smith.

It was popular from the start, but Smith thinks it was Tiegs’ cover that made it a phenomenon. However, it was Kathy Ireland in a white strapless bikini in 1989 that remains the best-selling cover.

“I’ve done many, many, many different covers in the fashion world … but never had as big a splash as Sports Illustrated,” said Heidi Klum, the cover model in 1998. “I went to ‘(The Tonight Show with Jay) Leno,’ the morning shows in New York and LA — it was a huge thing — suddenly I became a household name,” she said.

But more than the fame, Klum said she appreciates from SI the professionalism shown to a relatively untested model wearing next to nothing. “I had wanted it to be so good. I’d arch so hard … but they’d say, ‘Look sexy with your eyes. Don’t overpose. Be yourself and have fun.'”

There’s a balance between wholesome and sexy the editors are always straddling, without ever being sleazy, Hoffman said.

The magazine spends an average of three days shooting each model, each with an average wake-up call of 4:30 a.m. because the light is best at dawn, and have about 10,000 bathing suits to choose from.

And even with the outfits so small, SI spends an average of $2,000 in overweight baggage fees per location.

“The logistics are horrifying … but the Swimsuit issue is probably the healthiest of all the Sports Illustrated franchises, and it’s good to be with things that work, especially these days,” said McDonell.