Robert Dean Stethem, the son of Navy parents and the brother of Navy servicemen, loved his job as a Navy steelworker and diver because it involved plenty of travel and little likelihood of combat.

But Stethem, 23, a steelworker second class with Navy Underwater Construction Team 1 based in Norfolk, became a victim of the ongoing hijacking crisis in the Middle East, the Pentagon confirmed today. Stethem, who was returning from a routine repair assignment at a sewage treatment plant at a Navy installation in Athens, was the man slain Saturday by extremist Shiite Moslem gunmen who hijacked Trans World Airlines Flight 847.

"I talked to him a couple of weeks ago when he came to the school," said Patricia Collins, a social studies instructor at Thomas Stone High School in Waldorf, where Stethem was a 1980 graduate.

" . . . He told me he was afraid to go to Central America," Collins told reporters yesterday, "because of all the fighting . . . He was very glad to be in a job he could travel in. That's what's so . . . ironic."

Stethem's father, Richard, his cheeks streaked with tears, stood in front of his split-level home in Waldorf this afternoon after getting confirmation of the death from Navy officials. He told reporters he was proud of his son.

"He was a proud kid," said Stethem, 49, who himself spent 26 years in the Navy before retiring. "He was very proud of being in the service. We probably need more fighters like him."

The identification of Stethem, a Seabee, cleared up three days of confusion and conflicting reports. Initially, it was reported that the victim was a U.S. Marine.

According to flight attendants who were aboard Flight 847, Stethem was badly beaten by the hijackers before being shot and dumped on the Beirut airport tarmac Saturday. Richard Stethem said tonight that the family did not know why their son had been singled out by the terrorists.

At a press conference in New York Sunday, head flight attendant Uli Derickson said she didn't know what prompted the hijackers to kill the man.

Katie Tucker, a spokesman for U.S. Rep. Roy Dyson (D-Md.), said yesterday that identification of Stethem was delayed because of the condition of the body. She said his face was apparently "severely deformed" in the beating he received. She said Stethem's friends were asked to identify his body at the U.S. Air Force Base in Torrejon, Spain, and that fingerprints and medical records supplied by the Navy also were used.

Stethem's body is scheduled to arrive at Andrews Air Force Base about midday Tuesday.

Stethem came from a family immersed in the military. His mother Patricia, 49, spent her career in Navy administrative posts. His older brother, Kenneth, 24, is in the Navy in Norfolk. His younger brother, Patrick, 19, has signed up to enter the Navy in November. Only his sister, Sherry, 27, has not signed up for the military.

Richard Stethem said he had not encouraged Robert to enlist, but that his son signed up for a five-year stint in December 1980, six months after his high school graduation.

The Stethems last talked to their son two weeks ago, when he telephoned from Kennedy Airport in New York where he was awaiting a TWA flight to his assignment in Athens.

Friends and neighbors in Waldorf, a Charles County town of about 26,000 where the Stethems have lived for 19 years, described Robert Stethem as quiet, polite and athletic. Nicknamed Robbie, he played defensive back on the high school varsity and junior varsity Cougars football team and often organized neighborhood games.

"He was not a troublemaker," said neighbor William Fisher.

Stethem did occasionally display the high spirits of youth, however. Neighbor Jonathan Reid, 20, recalled the time several years ago when Stethem and some other boys climbed a local water tower several stories high. "Robbie didn't get caught," Reid said.

Neighbors said Stethem had described his Navy experiences as fun. He apparently enjoyed his job, which involved diving work on underwater construction projects.

Patrick Stethem, his younger brother, said today that Robert's death only strengthens his desire to enter the Navy. "I signed up last week before the plane was taken," he said. "If anything, I plan to be better."