'Tis better to err on the side of caution, of course particularly when it comes to boats and water, but can be boring too.

Manuel Munoz-Carrasco is something of a daredevil.The book says that Class IV whitewater is "generally not possible for open canoes." That's the kind of water Munoz warms up on.

He considers the Youghiogheny in spring runoff a reasonable challenge, solo in a 15-foot Grumman. For most people that river provides more than enough thrills in a rubber raft, the safest river craft.

So when Munoz suggested a spring family canoe trip in the mountains his invited colleagues imagined children torn screaming from their boats, bobbing through the riffles and into what paddlers gloomily call "terminal hydraulics." t

"no, no, no," said Munoz. "we will go to an easy river. A scenic river.

Someplace for the children."

Ever the radical, one way or the other, he erred this time on the side of wretched caution.

He rattled through his books of recommended streams and came up with one called Opequon Creek, which is in the Shenandoah Valley near Winchester. The book said it was a quiet, scenic stretch of Class I water, nine miles from put-in to takeout through pretty farm fields and rolling hillsides.

It was quiet all right, until four boats and five kids and six adults and a Dalmation in heat began thumping and crahsing along rocks barely covered by a trickle of spring water. Class I indeed. Class I rocks.

"oh," groaned Munoz after the first mile. "I am tired. This is work."

The highlights of this ill-fated voyage turned out to be only two. After an initial spell of complicated maneuvering to get around blown-down trees and catttle fences strung across the little creek (hardly high sport) the four boats approached a bend and heard staccato reports of rifles and shotguns being fired ahead.

They stopped above the bend and plotted a course. "let's send the kids through first," someone joked. "smaller targets."

But a boatload of adults finally braved the bend. They found a shooting range on the very banks of the creek, where earnest men in earmuffs were practicing up for the next hunting season.

"yo,". shouted the paddlers.

"bang. Kerblam. Ping," came the reply.

There was nothing to do but plunge on, which the paddlers did, and were fortunate enough to be spotted by the shooters as they rounded the last turn before the bullet landing zone. The shooters pulled off their earmuffs. "hey," they yelled.

"yo," yelled the paddlers.

And so it went. Four boats, 30 "Heys," 50 frantic "Yos" and the first great challenge was passed.

They crashed and bumped and cursed over another two miles of rocks.

The obstacles became fewer, but the water seemed shallower with each mile. Then came the crowning touch. They rounded another bend and found, parked in the middle of scenic little Opequon Creek, a 1971 AMC Javelin SST with fresh 1980 tags.

"himm," said Johnny Munoz, the trip leader's young son, "maybe he thought it was a car-wash."

The Javelin was deserted. No one asleep behind the wheel. It had been there a few days, presumably the remains of an ill-conceived attempt to ford the stream during higher water. The paddlers all longed to have been there then.

Nine miles may not seem like a long stretch, but it's a burdensome and noisy way to go in an aluminum boat over rocks. Usually white water paddling consists of pleasant stretches of gentle water punctu- ated by the sounds of fast riffles ahead. Adrenalin pumps, the stern paddler stands up and scouts the rapids and then there is an exhilarating plunge into uncharted water.

But every time this crew heard fast water ahead, all they could do was groan.

Not the greatest trip Munoz ever planned. Still, this is barely the beginning of white-water season. Canoeing is good sport and if self-styled voyages sometimes fizzle, there are other times when they are simply perfect. Even bad trips are fun by the time they're over, particularly for the kids.

Washington has more canoeists per capita than any other city in the country, which makes sense because it's within striking distance of some of the finest canoeing water in the country.

It also has the finest canoeing organization in the country, the Canoe Cruisers Association, which organizes weekend canoe voyages throughout the season for all levels of paddlers.

CCA can be counted on to scout upcoming streams to avoid the kind of low-water deb .acle at Opequon, or its more dangerous corollary, a raging flood. And CCA always welcomes new paddlers, whether they've sent in the $10-a-year fee that makes them club members or not.

This weekend CCA will lead day trips for novices and intermediate paddlers on Cedar Creek near Strasburg, Virginia, and for intermediates and advanced on the Potomac near Petersburg, West Virginia. The following weekend there are trips to the Appomattox and James Rivers for intermediates; the Hughes River for novice/intermediates; and Cedar Creek and the Anaheim River for novices, plus two hard-core slalom and whitewater races.

And so it goes, week after week.

CCA is the place to look for good trips. There are 2,000 members now and space for plenty more. For membership information write to CCA, Box 572, Arlington 22216.

CCA also runs classes to teach people to paddle. They range from remedial courses on the C&O Canal for complete know-nothings to Red Cross basic canoeing ($5; 20 hours classroom and on the river); a whitewater course, also for $5 with a major river trip as the graduation service); and special classes in kayak and covered canoe. For information on these courses write Classes, Box 4116, Colesville, Maryland 20904.