The wife brought a cup of coffee to the husband, who was at the wheel, little realizing that simple act would lead to a whopping insurance claim."

Derek Scorer, a marine insurance agent in Annapolis, was describing events that led to big trouble for the 40 foot houseboat that had jst left Occoquan Bay for a cruise on the Potomac.

The day was fair; the water was smooth," Scorer said. "The husband held the coffee with one hand and steered with the other. Suddenly the boat struck something in the water and the engine outdrive popped up. The engine began to race, to run away."

At that the skipper became befuddled. He couldn't decide whether to drop the coffee or let go the wheel so he could get a free hand on the throttle. He stood there, transfixed, and in seconds the engine was destroyed.

"What I see more often than I like," Scorer said, "are claims where asininity plays a large part. That was one such case. Another involved a man who decided an easy way to winterize his 24-foot cruiser was to plug an electric space heater into an outlet on the boat in the next slip."

Eventually the severe cold of last winter put so much strain on the electrical system of both boats that a circult breaker opened, cutting off the current.

"That lunatic had been too bone-idle to even drain the water from his engine or to put in antifreeze," said Scorer. "Naturally the engine froze. Repair costs came to $1,980. The man just didn't think."

Scorer said another example of minimal thinking touched a seven-boat raft-up last August. Rafted boats are boats tied up alongside each other with the anchor from the boat in the middle holding for all. Scorer said boats anchored that way are particularly vulnerable to damage from high winds. "The boats bash agains each other and the rigging and spreaders are put at risk. Rafted boaters should be especially responsive to the threat of bad weather."

But the seven rafters ignored a severe thunderstorm warning that was on the radio all day. When they found a good-looking cove on Chesapeake Bay's Eastern Shore, the raft - a friendly and natural congregation for sailors who want to rehash the day's sail - formed at once.

Scorer said once the hook was down the radio was cut off and the champagne was opened. At 5:30 p.m. the happy hour was assaulted by 70-knot winds and drenching rains. Before it could be disassembled the raft was blown out of the protection of the cove with the boats banging all the while. Not one boat escaped damage; insurance claims every case exceeded $1,000.

Some of the claims Scorer investigates border on the unbelievable. He cited the case of the chartered 41-foot Morgan sailboat that passed under Chesapeake Bay Bridge last May.

The skipper "could have taken the center span and had more than a 100 foot margin," Scorer said. "He could have taken any number of spans to the right or left and been all right, too. But no, for some strange reason he chose a span far away from the center and failed to clear it by three feet. The forestay snapped and both the mainmast and the mizzen toppled. Fortunately no one was hurt. Repair costs came to $700."

Scorer said he is seeing an upsurge in claims based on the failure of boaters to realize how vulnerable the boat is when the forward hatch is open. He remembers one recent incident involving a man who, on the basis of his years of boating experience, should have known better.

"He was driving his $13,000 power boat through rough water with the forward hatch not properly secured. A wave broke over the deck, opened the hatch and flooded the forward compartment. The boat had to be beached.Damage came to $1,850."

Scorer, who owns a Gulfstar 44-foot motor-sailer and who has sailed for 50 years, is convinced many skippers fail to get decent boating educations.

"Would-be sailors require some instruction before they can make a sailboat go," Scorer said, "so they usually get somebody to show them the ropes. But power boaters tend to go off without really knowing very much about it. They drive cars and they think it's as simple as driving a car. It isn't.

"Ways to prevent the incident I've mentioned are routinely taught in the basic boating courses of the U.S. Power Squadrons; the Coast Guard Auxiliaries the Red Cross and many others. They are full of specific information on how to read a chart, how to winterize a boat, how to handle it in rough weather - the whole bit.

"It's all practical stuff directed toward making a boater careful and cautious. The courses don't cost anything and if you pass you can get up to a five per cent discount on insurance premiums." CAPTION: Picture, Divers work to refloat the Crystan Catfish that ran onto a reef near the end of Newport-Bermuda race as owner John Hunt tried to compete alone. But the $150,000 sloop is expected to be a total loss.