On a recent Sunday morning on the Magothy River, Dick Carey had his eyes on the water at Dobbins Hill reef, located near Dobbins Island.

Two heads with goggles and masks appeared from beneath the surface.

The divers — in search of oysters as part of an effort to monitor the health of an oyster reef — hadn’t found anything.

Scott Hagedorn went down next. About 18 minutes later he surfaced with a cluster of oysters in hand.

“I scoured the whole damn bottom for that,” Hagedorn said.

More were brought onto the boat to be measured and checked for spat and dead oysters.

The divers were part of an all-volunteer team for the Magothy River Association, and are trained in how to work in low-visibility conditions.

“It can go from essentially no visibility, all the way up to maybe two feet,” said Carey, who leads the team.

Divers say they would love to actually see the river become clear again — and volunteering on the team is a chance to help reach that goal.

Hagedorn, who lives in Montgomery County, said he volunteers for the program because it is a reasonable effort to re-establish an ecosystem that’s having difficulty surviving.

“The Magothy River suffers from a lot of pollution issues just like anyplace else along the Chesapeake,” Hagedorn said.

Paul Spadaro, president of the Magothy River Association, said the oyster diving team has been in place since 2001.

Using a 1/3-meter quadrant, the divers take samples and extrapolate the approximate number of oysters on each reef. The oysters are also measured, as is the water quality at each reef.

The count collected that day revealed a rate of 9,000 oysters per acre, Spadaro said. The reef is roughly 3 acres. That’s a pretty low number, he said.

In the mid-19th century, oysters at another reef, Rock Point, were so plentiful they formed an island of oysters, Spadaro said. Over-harvesting damaged that population.

“The reality is we ate the oysters,” Spadaro said.

The Magothy doesn’t have a strong showing for oyster spawning, Spadaro said. According to the National Oceanic and Atmospheric Administration, oyster spawning is salinity-dependent, and less common when salinity dips below 10 practical salinity unit, or psu.

Sunday in the Magothy the water near the Dobbin’s Hill reef was about 8 psu.

“Finding spat above the Bay Bridge is like the Holy Grail,” he said. “Development has pushed the salt water wedge to the south.”

The river has five oyster reefs: at Chest Neck Point, Rock Point, Ulmstead Point, Dobbin Hill and Persimmon Point.

The divers make four or five trips a year, Spadaro said, and also help with maintenance at the sites — on another Sunday they would attach a marker that indicates where one of reefs is located. Spadaro said they mark the reefs because they’re good habitat and a good resource for recreational fishermen.

One of the big takeaways from 16 years of oyster diving has been that there is an initial shock period for the oysters that are placed in reefs on the Magothy, Spadaro said. About half of the oysters die off within the first few months of placement.

But that’s not the only thing they’ve learned.

“Once you get over that initial shock and the oysters survive a year or two, they will survive five to 10 years,” Spadaro said.

Oyster diseases are absent in the Magothy, Spadaro said, which that gives the oysters there an edge in potential survival.

The diving program is self-supporting. The divers volunteer and bring their own equipment.

Sparado said that in addition to measuring the oysters present at the reef, divers will double-check marked edges of each reef to ensure that when additional spat is added it is truly going onto oyster shells, not into the mud.

What separates the Magothy’s diving program from others is the people, Spadaro said. “We’re consistent, and this is our home,” Spadaro said.

For the group’s leader, Carey, who is 80, diving is a passion. Carey was leading the group, but didn’t dive Sunday.

The team has shrunk over the years, from roughly 45 volunteers to about 20, Carey said. Spadaro said they are seeking new divers, and also looking for leader to take over for Carey when he steps down.

For more information on the Magothy River Association and its program, go to magothyriver.org.

Many of the same volunteers return year after year to dive on the oyster reefs. That’s the case with Hagedorn, who has been with the group since the beginning.

He says he sees neat stuff while diving, such as rays feeding on the oysters and rockfish, he said.

“It’s fun to go down there and see what’s happening,” he said.

rpacella@capgaznews.com