SURFING ON the Eastern Shore is less than the royal sport of kings. In fact, it's mostly illegal.

A case in point: A father and his daughter walking Rehoboth Beach at sunrise watched a young surfer unceremoniously take leave of his surfboard, the surfer lying in one direction, the board in another.

When the surfer went to recover his board the father was there at the water's edge to greet him with these sharp words: "If that board ever hits my daughter, I'll sue you for everything you've got."

The surfer looked from the man to the board and said, "This is it, the board is everything I've got."

The angry parent was exercising genuine rights; the surfer should not have been in those waters. Among other taboos in the area, surfing is forbidden.

It is, however, the general practice that this regulation is enforced only from 10 a.m. to 5 p.m., when the lifeguards are on duty. Thus the surfers are on the water at daybreak and twilight to avoid conflict with the bathers and local authorities. At Ocean City, five areas are set aside for surfers.

A number of reasons are given for outlawing or tightly restricting surfing. The most plausible is offered by Bayard Coulter, town manager of Bethany Beach, where surfing is strictly forbidden:

"It's a matter of liability. If we allow it and a bather is hit by a flying surfboard, then we are sued."

Surfers blame their unpopularity on a few nomads among them who are into drugs and other subculture phenomena and who have in the past slept overnight on the beaches and left them littered.

Officials found the lifestyles of some itinerant surfers offensive, and in resort areas that are advertised as "family beaches," spaced-out surfers and their groupies made for bad publicity.

"Surfers, too, are notorious for spending as little money as possible," said Andy Beck, a skilled surfer who manages the Caravan Surf Shop in Bethany Beach.

But the situation is changing and surfing seems on the upswing, according to Dave Dalkiewicz, president of the Delmarva Division of the Eastern Surfing Association. He says much of the change results from the spreading popularity of skateboarding. Skateboard enthusiasts readily adapt to surfing.

Dalkiewicz has improved surfer liaison with local officials. His association has only 100 members, but it is growing rapidly.At least 500 surfers converged on the Eastern Shore this summer and about 100 diehards in wet suits surf through the fall and winter months.

Surf movies sponsored by the ESA in Ocean City's convention hall have played a full houses this summer and it was a healthy-looking, clean young crowd.

More good public relations emerged from the recent surf qualifying tournament off Ocean City's 145th Street beach. The competition was for a chance to go on to regional action off Cape Hatteras in September.

The surfers competing in five classes from ages 12 to 21 (and some up to 30) were far from subculture types.

Some caught up in the Eastern Surfing Association have joined with environmental forces to protect the beaches. Dalkiewicz has urged the members "to try to stay informed through the media."

"Each of us," he urged in his folksy newsletter, "can have a voice in this fight, if the effort is made."