The body of Natalie Wood, who started her career a child star and grew into an actress who played leading roles in such hits as "Rebel Without a Cause," "West Side Story" and "Gypsy," was found Sunday floating in the ocean near Catalina Island off the California coast. She was 43.

Officials said Miss Wood apparently drowned, but that an autopsy will be conducted to determine the cause of death. The actress and her husband, Robert Wagner, a star of the "Hart to Hart" television series, were spending the weekend on Wagner's yacht.

Miss Wood was reported missing from the yacht about midnight Saturday, officials said, shortly after she, Wagner and some friends had returned from dinner on the island, located 26 miles southwest of Los Angeles.

This conflicted with an earlier statement by island harbor authorities who said that, after dinner, Miss Wood disappeared while trying to pilot a small inflatable power boat back to the yacht alone. Sheriff's deputies said last night that this report was incorrect.

After an 8-hour search, her body was found about 200 yards from shore near the power boat, which she apparently had used to leave the yacht.

"She went out in the boat by herself and slipped off or fell off or jumped off," said Lt. Gary Crum of the Los Angeles County Lifeguard Service. Officials said an investigation was continuing.

Miss Wood was working on the filming of "Brainstorm," a Metro-Goldwyn-Mayer production in which she starred with Christopher Walken, Louise Fletcher and Cliff Robertson, at the time of her death.

The death of another star more than 25 years ago had an important effect on Miss Wood's own career. He was James Dean, the teen-age idol of the 1950s. Shortly after the completion of "Rebel Without a Cause," in which he played a juvenile delinquent, he was killed in an automobile accident. His death attracted enormous publicity for the film, in which Miss Wood, then 16, and Sal Mineo were the other stars.

"When Jimmy Dean died, the teen-agers made him a martyr and latched on to Wood and Mineo. . . . Anyway, the fan mail began coming in. So we signed Natalie," said a Warner Brothers executive.

Miss Wood was nominated for the Academy Award for best supporting actress for her work in "Rebel." In the next 10 years, she made a number of notable films, including "Marjorie Morningstar" (1957), which was based on the Herman Wouk novel about a Jewish girl in Protestant society in New York and in which she played opposite Gene Kelly; "Splendor in the Grass" (1961), in which she played opposite Warren Beatty and for which she received another Academy Award nomination; "West Side Story" (also 1961), the Romeo-and-Juliet story set among the street gangs of New York; "Gypsy" (1961), in which she portrayed Gypsy Rose Lee, the legendary stripper; "Love With the Proper Stranger" (1964), with Steve McQueen, which got her a third Academy Award nomination; "The Great Race" (1965), with Jack Lemmon and Tony Curtis, and "Inside Daisy Clover" and "Penelope," both in 1966 and both milestones in Robert Redford's rise to stardom.

Miss Wood's television appearances included "Cat on a Hot Tin Roof," which was produced by Sir Laurence Olivier and for which she received an Emmy nomination, and "From Here to Eternity," for which she won a Golden Globe award.

Along the way, Miss Wood made a solid if unspectacular reputation. She was petite, dark-eyed and beautiful, a nice girl, but a bit too flashy, perhaps, to play the girl next door. "Maybe I'm not given credit for being an actress by the press," she once said, "But the industry takes me seriously. Most directors know I haven't forgotten I'm an actress." The Harvard Lampoon, an undergraduate humor publication, twice gave her its "Roscoe" award for the worst performance of the year. In 1966, the magazine renamed it "The Natalie Wood Award" and the actress was on hand for its presentation.

Her own disclaimers and the Lampoon notwithstanding, Miss Wood could go along with such stunts because her talent had become recognized. Writing of "Splendor in the Grass," which was based on a William Inge play about a girl in a small Midwestern town who loses the local rich boy and her sanity and who eventually develops a new understanding of herself, a reviewer in Newsweek magazine said:

"After years of vacuous popularity Miss Wood suddenly finds herself being taken seriously."

Bosley Crowther said of the film in The New York Times: "Miss Wood has a beauty and radiance that carry her through a role of violent passions and depressions with unsullied purity and strength. There is poetry in her performance."

Apart from such praise, Miss Wood also garnered a fortune. At one time, she commanded $250,000 for each film. In 1969, when she appeared in "Bob & Carol & Ted & Alice," a critical and popular success about wife-swapping in Beverly Hills, she received a percentage of the picture's gross. Her earnings from the venture were said to be $2 million.

Despite her fame and fortune, all was not easy for Miss Wood. At one point she was suspended by Warner Brothers. The studio said the dispute involved salary. Miss Wood said the problem was parts.

"You get tough in this business, until you get big enough to hire people to get tough for you," she said in an interview about that time. "Then you can sit back and be a lady."

Born Natasha Gurdin in San Francisco on July 20, 1938, Miss Wood was one of three children born to Russian immigrants. Her father, Nicholas Gurdin, was an architect who turned to set decoration in this country. Her mother, Maria, was a former ballerina. When Natasha was 4 years old, the family moved to Santa Rosa, Calif. It was there that the child and her mother got bit parts in a film called "Happy Land."

The director, Irving Pichel, remembered the little girl's walk-on when he was making "Tomorrow Is Forever" in 1946 and gave her a part. She played a child who is adopted by Orson Welles, who later said that "she was so good she was terrifying." The film's producers changed her name to Natalie Wood.

Miss Wood was put under a contract earning $1,000 a week. In 1946, she appeared in "The Bride Wore Boots." A year later, she played the little girl who came to believe in Santa Claus in "Miracle on 34th Street," which has become a perennial favorite.

In 1956, Miss Wood married Robert Wagner after a widely publicized romance. The couple settled down in a Beverly Hills mansion equipped with "his" and "her" swimming pools. The marriage ended five years later. In 1969, Miss Wood married Richard Gregson, a film executive. They had a daughter, Natasha. That marriage ended in divorce. On July 16, 1972, Miss Wood and Wagner were remarried on a yacht off the California coast. They had one daughter, Courtney.

"We had each other in our youth," Miss Wood once said of her relationship with her husband, "and now we have each other in our prime."