Along the banks of the river, Cynthia Crossen pulled out her magnifying glass and showed her 8-year-old volunteer the feathery gills on the lower side of the mayfly's body.

"Cool!" Forest exclaimed, then waded back into the water for another go.

Sunny skies brought out scores of children and adults Saturday for the annual Haw River Festival in northern Chatham County.

Crossen, a technical writer, became a passionate guardian of the Haw in 1994 when she helped found the Haw River Assembly. Today she coordinates the Haw River Watch Project, checking for freshwater invertebrates she calls "critters" to monitor the health of the river.

The rushing water filled her ears as Crossen set up her gear: nets, plastic tubs, and laminated identification sheets. From the bridge above, muted sounds from the Rootzie Band drifted down to the water.

To get to where Crossen stood, you had to cross the bridge and follow a narrow path down a steep bank to Bynum Beach. The strip of sand provided the perfect landing for the free short canoe rides offered at the celebration.

Soon after setting up her nets, Crossen had three young volunteers: Forest and his brother Emerson, 11, from Bear Creek; and their friend Anthony Peoples, 12, from Back Creek.

It was a biological treasure hunt as the boys grabbed nets and tubs and followed Crossen's careful instructions.

Anthony waded out to where boulders and large rocks broke the current. He pulled a net through the water and strode back ashore for Crossen to identify his specimens: a stonefly, fingernail clam and aquatic worm.

Emerson found a caddisfly and learned how to find its fluffy gill tufts, using Crossen's water-proof chart as a guide.

The three friends regularly hunt in a creek in their back yard.

"We find crawdads and tadpoles all the time," Emerson said. "It's fun to look under the rocks and see what's living there. Bugs are good for the environment 'cause they help keep it clean!"

Crossen's chart places insects and crustaceans in three categories and assigns points for each discovery based on their sensitivity to pollution.

After the critter watch ended, Saturday's score came in at 22 points.

"That's the high edge of excellent, which is a good score," Crossen said.

She would have liked to find more of each organism. But she was glad to see so many different critters,

"Finding something from all three groups indicates a healthy river," she said. "If you only found organisms from one list, you'd start to get concerned."

As for the three friends, they had already left the water in search of their next adventure.

"Time for food!" one of them yelled as they scurried up the bank and disappeared.