I was working along a little rock ledge on the Patapsco River the other day, searching the stream bed for places a smallmouth bass might lurk, when my foot found a nonconformity in the bottom.

Ker-splash!

It was your basic uncontrolled nose dive with fly rod and, if there were any judges watching from the windows of the Washington flour mill 50 yards upstream, they no doubt gave it a 9.6 for artistic merit, except of course for the Russian, who is hard to please.

I mostly was worried about the rod, which was borrowed and expensive and did little to cushion the fall. Then I worried about the wallet, which was a violation of Rule No. 1: always remove your wallet before wet-wading, because they don't call it wet-wading for nothing.

The latest warm spell, combined with a season-long drought, has left the Patapsco, Potomac and other area rivers low and warm enough to wander around on foot in pursuit of bass and panfish, and that means wet-wading season is in.

This is terrific sport, if you don't mind a good dunking, and there's plenty of it close by.

I've had excellent luck wading and float-fishing in the Potomac, Shenandoah and Rappahannock rivers within an hour or two of Washington, but when Dick Blalock called to say there was fine wading on the Patapsco, it was news.

The Patapsco to me always has meant the gutter that drains fetid Baltimore. But it turns out that if you get upstream of the city it's still a lively little unspoiled river.

"This is about as close to the Catskills as you get around here," Blalock said as we clambered down the bank just below the 150-year-old flour mill in the heart of Ellicott City.

It did look good. The water was clear and reasonably cool as it tumbled over rocks with a refreshing gurgle. The banks were steep and emerald green with vegetation. There was some junk strewn around, but Blalock cautioned not to disturb the refrigerators and tires. "That's where the bass hang out," he said.

According to Chuck Allen, who runs the Orvis fly fishing shop here, the Patapsco is a consistent producer of smallmouth and bluegills for folks who fish it regularly. "I had one guy that used to come in who worked for the Baltimore Symphony," he said. "The Patapsco was the only place he fished. He'd go three or four times a week and catch anywhere from 50 to 150 a day."

Blalock and I did nowhere near that well, but we didn't have a lot of time and the time we had was the worst of the day. It was high afternoon when we fished and, in the glaring heat, the bass were back under rock ledges, staying out of the sun.

You could see them drift out occasionally and eye our offerings, but generally they weren't taking. Neither were the bluegills, which scattered from the hot shallows at the hint of intrusion.

But what life there was in the stream! Crawfish scurried out from under rocks, minnows skittered along the surface, a mallard burst out of a little cove, bugs and flies hovered around.

And in the scalding afternoon, what gentle pleasure in finding a waist-deep spot, casting awhile, then simply bending the knees to descend, neck-deep, into the cool, purling water.

"I look at fishing the same way I look at poker," Blalock said later, explaining why he wasn't disappointed at our meager catch. "In poker, you might have the most beautiful straight flush in the world, but it doesn't do you any good if the other guys don't want to play.

"Today we had a good hand, but the fish just didn't want to play."

The accompanying list of wet-wading spots around Washington should provide an idea of where to go. Now here is what to do, and what not to do:

*Don't wade alone. You probably will fall, and you could conk your head and drown.

*Be careful. River levels change fairly rapidly, so don't get yourself in a spot you can't get back from if the water comes up.

*Carry a staff of some sort and use felt-sole shoes for good traction. If you're a bad swimmer or uneasy in the water, wear a life vest. Polarized sunglasses are a help in seeing the bottom and the fish.

*Good flies for smallmouth and bluegills: Black marabou streamers, crayfish imitations, poppers for slack water, woolly buggers and hair bugs.

*Good lures for spinfishing: Small Rapalas, Mister Twisters and Beetlespins, Mepps spinners, small crankbaits.

*The best times of day for summer fishing for almost all species are early morning and late evening. This makes a nice wade a good way to kill an evening, or something to do early, before work.

*For all-day wading, a good tool is a little boat, which floats you from one good spot to the next without worrying about access points.