Everyone knows gasoline and water do not mix. Perhaps the unhappiest marriage ever is the one between the internal combustion engine and the boat.

That was a lesson I had the happy opportunity to relearn last week aboard a small catamaran on the Chesapeake Bay.

I been intrigued with a little chartering outfit ever since it opened up at the base of the east end of the Chesapeake bay Bridge last summer. It is called Chesapeake Charters and offers Prindle catamarans and Windsurfers for rent by the hour.

Brian Eiland, the manager, offered a ride on a 16-foot Prindle any day when the wind was good. Last Wednesday, the marine weather [phone 899-3210] promised south breezes of 12 to 18 knots all afternoon. It sounded ideal.

All sailors know that the marine forecast is not always to be believed. We sat in Eiland's trailer office and chatted for an hour and a half, wating for the wind. It didn't come.

At about 2, he felt a whisper on his cheek and suggested we give it a try. "I'll have Dennie run you out for a quick lesson, then you're on your own."

Dennie, it developed, is 18-year-old Jane Denmeade Chambers, just graduated from the elegant Foxcroft School in Middleburg -- 5-foot-2 blue-eyed, tanned, athletic and distressingly attractive in a string bikini, which is what she was wearing. She is the Chesapeake Charters instructor for novices.

"I'm a novice, I'm a novice," I shouted.

To make a very long story short, we had an easy sail across the Chesapeake under a baking sun. Then at the mouth of the Severn the breeze quit entirely and out half-hour lesson stretched into a three-hour foray as we whispered home across the flat, calm seas.

We arrived at the Chesapeake Charters beach about suppertime, and just as we pulled the 300-pound cat onto the sand a wonderful breeze sprang up, gusting 15 to 20 knots from the south.

"I can't believe it," enthused Chambers. "We've got to go out again. You'll love it."

"Let's go, let's go," I said demurely.

So we were off again, streaking across the chop at a good 12 knots, the windward pontoon of the little twinhull craft slicing high in the air. "I love to fly a hull," shouted the win-whipped skipper.

We made Annapolis in 45 minutes this time, stopped for a Coke and then set out for home. The wind died, of course.

Which left us ghosting across the slick Bay at a half-knot while the sun turned orange and finally faded into black night over Annapolis.

And freezing.

We huddled close to share body warmth, watch the shallow rim of a developing moon overhead and I said a silent prayer.

"Thank you, Lord, for not putting an engine on this boat."

Of course, like all swords this one can cut two ways.

A few years back, a fellow we'll call Paul to save him heat had a sloop and a new lady friend, whom we'll call Tammy to save her heat.

Paul thought he would take Tammy for an evening cruise out the West River and into the Bay one weekday. It was a lovely evening with a sturdy breeze that looked as if it would hold up. He had an outboard but no fuel. He didn't bother to fill up. The evening looked promising.

They sailed to mid-Bay and watched the sun descent over the water. With it went the wind.

They were becalmed, utterly and completely. In the middle of the Norfolk-baltimore shipping lane. With no gas. And no running lights or anchor lights.

"We were supposed to go to Galesville for dinner," said the woman we'll call Tammy. "I was so hungry and so scared. The boat kept rocking. I was sure we'd get cut in half by a tanker. I couldn't sleep all night."

The man we call Paul, she said, spent the night sitting on deck and blowing on a pathetic little foghorn to warn the ships away.

Another boat was anchored not far away and the stranded pair hallooed for aid. "but, said Tammy, "tammy, "all they did was laugh at us."

Finally, in the morning, a cruiser passed by, stopped and parted with some fuel.

They were at the dock by 9:30, bleary-eyed and already a half-hour late for work in Washington. She called the office.

"Sure," said her boss. "That's a good one."