We have been transfixed by him for so long now, maybe we just forgot that the inevitable transformation was on its way. With this month's gargantuan Titanic, the surprise arrives: Boy wonder Leonardo DiCaprio, 23, has become a riveting leading man.

After specializing in such edgy teenage roles as a hipped-up Romeo and the mildly retarded brother in What's Eating Gilbert Grape? (for which he received a 1994 Oscar nomination), DiCaprio has sailed into adulthood on a $200 million action blockbuster. "I think Leo has a questing spirit," says Titanic director James Cameron, who spent three months convincing DiCaprio to come aboard. "He's an actor's actor. But great acting isn't necessarily about great angst; I had to convince him there was going to be enough of a challenge." That promise was kept on the set at Rosarito Beach, Mexico, where grueling conditions and production snafus included a near-fatal injury to DiCaprio's pet lizard Blizzard, which was run over by a truck. But even more critical to DiCaprio was capsizing his image as an exquisitely tortured teen. As Jack Dawson, a scrappy artist in love with society girl Kate (Sense and Sensibility) Winslet, he emerges as a confident, romantic charmer. "Absolutely awesome," Winslet calls him. "Leo's a natural, the actor of the century Nobody can get near him at this point." Those who do, says Martin Brown, producer of the 1996 update of Romeo and Juliet, find the unattached actor "intensely interesting to be around, very active and very much a live wire. He's astonishing." Particularly so in one Titanic love scene that Cameron recalls directing. "At the end I said, 'Okay, Leo, before this movie there was probably some Eskimo woman or woman in Borneo who did not want to drag you off to bed. After this, even she will want to.' "