To Kevin Sinnett, it does not seem as if 3 1/2 years have elapsed since he enrolled at the Naval Academy. Time has floated rapidly by, and Sinnett claims it has been fun.

"Looking from the outside in, I guess somebody would find it hard to believe I've enjoyed it here," said Navy's star senior basketball forward, who earned All-Met high school honors in 1975 while playing at St. John's.

Sinnett finds it hard to fault a single aspect of the regimented life at the academy and will continue in the service the five years he owes Uncle Sam after graduation.

"The regimented life style helps out in later life," said Sinnett, a shy, softspoken man who is perhaps the finest player in the academy's history."Plus, when I'm on the basketball court, I can forget everything about school and just enjoy myself."

Things haven't been especially enjoyable for opponents who have had to guard the 6-foot-6 senior. Sinnett has averaged 17 points per game during his career -- including an 18.1 mark last season and 20.4 currently -- has never shot under 50 percent for a season, and is 51 points away from breaking the academy's all-time scoring mark of 1,561, set during 1951-54 by John Clune.

It is Maryland's turn to try to stop Sinnett tonight, when Navy visits College Park for an 8 o'clock game (WJLA-TV-7).

"He's one of the smartest players we've ever played against," said American University Coach Gary Williams. "He's probably the smartest we'll see all year. Sinnett's not spectacular, just very sound basically."

Williams had good reason to praise the midshipman, Sinnett popped in 30 points early in the season ("It seemed like 60," said Williams) to lead Navy over the Eagles.

Sinnett also leads the team in rebounding, which he has also done the last two seasons, shoots better than 80 percent from the free throw line and, coming into this season, was Navy's second all-time field goal percentage shooter.

"Kevin's intensity is getting better," said Jack Williams, a Navy assistant coach. "He's shy, but he is beginning to come out of his shell, although not in a cocky way. In close games, he wants the team to get him the ball to get them back into the game."

Navy Coach Bob Hamilton had said before this season that his plan would be to get Sinnett the ball first and then let him decide on the next option.

But Sinnett does not want to hog all the action. "I don't think a team can win with one guy having to do it all," Sinnett said. "We've got others who can shoot it in. Plus, the defenses have adjusted, shutting off the inside."

When that happens, Sinnett is just as likely to get his hands on the ball anyway, off the offensive boards.

"Sinnett knows how to use position out there," said Gary Williams. "He's not a great natural jumper but often seems to end up with the important rebound."

Being the main man at the academy for the past four seasons has not infected Sinnett with a desire to continue his basketball career after his postgraduation stint.

"After eight years of high school and college ball, maybe it would be nice to have a break," said Sinnett. "I've looked at other guys here getting three weeks off for Christmas while the team stays around and practices and plays during most of the holidays. At any rate, I think pro ball would be out of the question."

Sinnett, however, may be premature in selling himself short.

"He played with some of the Washington Bullets this summer," said Jack Williams. "He went one and one with Greg Ballard and Mitch Kupchak and made out well."

The oceanography major, a consistent B student, will go to flight school after graduation and a June date at the altar.

Sinnett, an Annapolis native, chose the academy "because I had a lot of respect for the people involved with the Navy and was impressed with the education offered. Plus, I like the security of having a job guaranteed for five years after I finish school.

"That'll be enough to give me a good look at the Navy. And if I want to keep playing, the Navy has an interservice team."

Thus, it is with few regrets that Sinnett may soon end a sparkling basketball career that began with him making the 80-mile round trip from Annapolis to basketball-rich St. John's for four years -- arriving so early that he would often nap or study on the steps of the school before even the custodians arrived.

Sinnett long ago measured the difference between the potentially shortlived involvement in fun and games and the security of a solid start down the longer path of real life.

And, as few others are, he is cognizant of what it means.