Divers map Lake Ronkonkoma detritus

It's like an archaeological dig in the middle of Long Island -- except the treasure is buried underwater in Lake Ronkonkoma.

A team of scuba divers is tackling the detritus at the bottom of the lake with sonar technology and recording its findings in a public database -- then diving to scoop up the more intriguing objects.

Led by Bill Pfeiffer of Island Diving, about 50 volunteer divers started the project in April. The spate of rainy weather in June delayed the divers, who are now videotaping specific targets for identification.

"We did find several sunken boats, and we can tell just by sonar they are boats," Pfeiffer said recently. "We don't know what kind yet, but we can tell by the shape."

Pfeiffer, who grew up in Nesconset, spent a lot of time in the lake as a child. "I like diving here," he said. "There's so much interesting stuff to see."

He got the idea to map the lake bed when his friend Peter Canning, a member of the Coast Guard auxiliary, told him he'd gotten a new toy: a $3,000 sonar scanner system mounted to the bottom of his 18-foot patrol boat, the Jeanne Marie.

The quality of the sonar scan, which uses sound wave signals to build an image, is excellent, Pfeiffer said. "It can be very much like an actual picture," he said. "You can even see the ripples in the sand."

And while the divers get to partake in a fun adventure, their volunteer efforts also benefit environmental agencies and geologists who aren't able to get to the bottom of the lake, which is deeper than 60 feet in some areas.

The diving team is creating a detailed map of the lake bed, and also pledged to extract any items that could endanger the health of the water -- such as car batteries, Pfeiffer said.

"We're giving them all this data for free," he said. "Having this kind of research done on the lake can open up many millions of dollars" in research and government grants. "It's a community service," he added.

Some elected officials praised the group's efforts as pivotal in revitalizing the lake. "This is one of the many positives to come out of the Lake Ronkonkoma Task Force," said county Legis. John Kennedy (R-Nesconset) during a visit to the lake to check out Pfeiffer's work. "All of it is about reuse and reclaiming what used to be a major tourist center."

In the early 20th century, the lake was a popular vacation destination, with hotels, bars and restaurants built around beaches, and floating docks ringing the shore.

The diving team has mapped the remains of a floating dock, which still has the metal hoops that bound the long-disintegrated wooden barrels together.

Pfeiffer said he expects to find more relics from that era. "There are plenty of stories about Model Ts being pushed into the water. Every time I dive down here, an old timer comes over and tells me stories," he said.

Another startling find has been Christmas trees.

The state Department of Environmental Conservation used to run an artificial reef program in the lake in the 1990s, Pfeiffer said. "They tied cinder blocks to Christmas trees and sank them," he said. "After ten years or so, they get waterlogged and fall over."

Another oddity: "We're finding coconuts. Dozens and dozens of coconuts," Pfeiffer said.

The likely source, according to Pfeiffer: All the bars that used to serve pina coladas to vacationers, who would then hurl their coconuts into the lake.