TAMPA BAY — The Coast Guard cutter Joshua Appleby rocks gently from side to side, a sure sign that the 175-foot-long, Keeper-class buoy tender is under way.

"The weather conditions are a little windy," says Danielle Elam, project manager for the Coast Guard's Research and Development Center in New London, Conn. "I'm not sure if we are going to be able to do everything we want to today."

Still, she's hoping to get started on an experiment using the system of navigational buoys that boaters in Tampa Bay rely on for safety. The goal: Keep systems like these from destroying the very marine environment they're also designed to protect — a Catch 22 that came to a head recently in Puerto Rico.

In summer 2014, after dozens of ships ran aground in Guayanilla Bay, the Coast Guard installed two traditional chain-and-anchor buoy systems to mark the bay's coral reef and sea grass habitats.

The work succeeded in protecting against more groundings, the National Oceanic and Atmospheric Administration reported — but the chains also scoured out the once-thriving marine habitat.

Elam, 39, has traveled to St. Petersburg to see if the chain-and-anchor systems and the concrete blocks that hold them down can be replaced with an elastic alternative that expands and contracts.

The plan, estimated to cost $153,000, is to install three types of elastic mooring lines across five navigational buoys in Tampa Bay. But privately contracted divers do the installation work, and if the water is too choppy, they can't come out.

So Elam and the crew will face a choice: Head out and hope the seas calm by the time they reach their destination 10 miles away, stay closer to shore and do what they can, or scrub the mission for this day.

The Appleby motors out into Tampa Bay.

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The Coast Guard has been looking for a way to fix the problems caused by the chain lines for two decades.

The lines secure "aid to navigation" buoys, essentially traffic lights of the sea. Their number, color and light patterns point boat operators in directions that, among other things, help them avoid shallow water.

The color red and the even numbers signal the right side of a navigation channel as a boater enters from the open sea or heads upstream. Green and the odd numbers indicate the left.

The Coast Guard takes care of 131 buoys in Tampa Bay.

Once the systems are in, Elam says, the divers will come back every three months for two years to see if there is any damage to the seabed. But first they have to get them in the water.

"This is all new to all of us," says Elam, noting the challenges of coordinating the Coast Guard, private divers and mooring-line companies.

An hour into the journey, the buoy deck of the Appleby, named for a Sand Key lighthouse keeper who lost his life in the Great Havana Hurricane of 1846, is a busy place.

AC/DC's You Shook Me All Night Long blares from speakers as the crew prepares buoys and mooring lines for deployment.

Seaman Steve Jensen, 20, climbs atop a 22-foot-tall red foam buoy to install a number decal. Wearing a blue cloth mask, Jensen resembles a ninja as he fastens a safety harness to the buoy to keep from falling off as the Appleby rocks in the chop stirred by 20-knot winds.

The crew of 24 is mainly Coast Guard members born years after the song was recorded.

"I'm the music keeper," says Seaman Ryan McMahon, who at 20 calls himself an old soul. "My father, who was in the Navy, loved classic rock and now I love it."

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Just before 10 a.m,, the Appleby is headed west under the majestic Sunshine Skyway bridge. People gathered on the bow are silent in awe. About a half-mile later, the vessel stops.

"Looks like we are going for the short day," Elam says. The water, she says, is still too choppy for the divers.

Still, for the crew of the Appleby, there is work to be done — their normal job of swapping out navigation buoys.

First, they lift an old steel buoy out of the water and replace it with one of the new foam buoys stored on deck.

"Keep coming, keep coming," shouts Boatswains Mate 2nd Class Kellen Zanandrie, 30, as a crane operator lifts a foam buoy — 16 feet tall and weighing 3,600-pounds — then deftly maneuvers it into the water.

The operation completed, they travel west with the old steel buoy on deck to a point midway between MacDill Air Force Base and the Mosaic phosphate mound, where another steel buoy is sinking.

They repeat the replacement operation, this time swapping one steel buoy for another, and lift the sinking buoy on deck for the return to St. Petersburg.

All the while, the crew holds out hope that the Appleby can return this day to the spot west of the bridge where they had just dropped the foam buoy — and meet up with the divers there so they can finally attach the elastic mooring.

But the Tuesday winds are still too stiff. The experiment is scrubbed for the day.

"We are here until Thursday," Elam says. "Hopefully, the weather will cooperate."

On Wednesday, they try again, with similar results.

But the work is important. The decision is made to keep Elam and her team in St. Petersburg another week to try yet again.

Contact Howard Altman at haltman@tampabay.com or (813) 225-3112. Follow @haltman