´╗┐Dozens of toy ducks and water bottles floated in Alexandria, Va.’s Chinquapin pool recently, as the SS Jaws joined nine other underwater remotely operated vehicles (ROVs) to capture them. More than enjoying a fun day away from school, ROV operators — sixth-graders at Alexandria Country Day School — were conducting experiments in tackling waterway cleanup.

The project began with students’ concerns about environmental issues, said Alexandria Country Day science teacher Alison McDonald.

“There was a lot of talk about plastic straws and other throwaways,” she said.

That led to learning about scientific efforts to decrease ocean trash.

“While it’s tough to say exactly how much plastic is in the ocean, scientists think about 8 million metric tons of plastic enter the ocean every year,” notes the National Oceanic and Atmospheric Administration’s ocean plastics guide. “That’s the weight of nearly 90 aircraft carriers.”

Inspired by ROVs tackling ocean debris, students consulted SeaPerch.org, an educational underwater robotics program. Teams used drills, pipe cutters, vises and wire cutters in designing “Sea- Perch ROVs” — about the size of a 12-inch cube — to collect plastics.

PVC pipes formed framing, plastic netting enabled scooping and pool noodles provided flotation.

Matthew Bearce, 12, of team Ruptured Duck, said, “We did everything — built motors, stripped wires, soldered parts — and kept adjusting all until it worked.”

The ROVs were built in the classroom but couldn’t be fully tested until students took them to the pool. Designs incorporated their understanding of water’s buoyancy, a force that makes things float.

“We had to drill holes in the pipes to allow air and water in so it wouldn’t just float on top,” said Jane Naegele, 11, of SS Jaws. The weight of pipes and netting determined flotation needed, while small propellers allowed control of vertical and horizontal movement.

Inaya Usman, 12, said her team debated the netting’s shape.

“We only had sides first, but decided to add a top to keep the debris in,” Inaya said.

About half of the teams added a floor to their ROVs.

Sora Ishihara, 12, said his team, Good Boi, used only deep sides and a top.

“It’s a study in buoyancy,” he said. “Ducks float, so we wouldn’t need a floor to keep them in.”

Communication was constant and encouraging as teams guided their ROVs through tasks at the pool’s deep end. The challenges required the ROVs to collect debris from within a concentrated area, collect debris floating across a large area, join two SeaPerches together using a pool noodle, and guide ROVs through vertical and horizontal hoops.

The ROV exercise wasn’t a competition, but a self-test of each team’s design and maneuvering ability. Good Boi collected the most ducks (40) in one run. “I thought we’d come to the pool and everything would work perfectly,” said Vivian Kocsis, 12. “It didn’t.”

Some ROVs sank, some tilted to one side and some had control problems. ROVs with floors often needed adjustment so openings were at the right scooping level. Students patiently tackled these problems on-site.

“A mistake is not the end of the world,” said McDonald. “Fixing it builds confidence.”