Thousands of traffic signals on the Chesapeake Bay from the mouth of the Susquehanna River to the entrance of the Atlantic Ocean lead cargo ship captains, commercial fishermen and recreational boaters out of harm's way.
When they go on the blink, transportation officials call on the ANTs.
A dozen men and women at Baltimore's Coast Guard station make up the Aids to Navigation Team, responsible for maintaining buoys, markers and lighthouses. They change light bulbs, scrape and paint metal, and bang out dents caused by sloppy seamanship.
The team ensures that range markers — powerful beams of light that act like runway lights for freighters and tankers approaching the port of Baltimore — are in the best location to catch the attention of bay pilots. They also help recreational boaters navigate the "skinny water," shallow areas in the bay and entrances to tributaries, by deploying red and green numbered buoys that bob like empty cans.
And they do it all on an annual budget of $104,000 that covers everything from office supplies to the lamps in the lights.
"They're the little team that can and does," said Mark O'Malley, who was the Coast Guard's captain in charge of the port of Baltimore before becoming head of the state's boating services program. "What ANT does is not glorious. Nobody notices them. But without them, we wouldn't be as safe."
A 2011 University of Maryland study estimated the annual impact of recreational boating on the Maryland economy to be about $2 billion and responsible for 35,077 direct and indirect jobs.
Port officials praised the Coast Guard teams as vital to the port's success. The port is directly responsible for about 14,630 jobs and supports 108,000 related jobs, according to state estimates. It generates $3 billion in wages and salary and more than $300 million in state and local taxes.
"They are essential to keeping our channels marked and operable for the safe passage of the massive cargo and cruise ships that result in the port being one of Maryland's largest economic generators year after year," said Dave Blazer, the Maryland Port Administration's chief of dredged material management.
The Baltimore team covers Maryland's portion of the bay with the help of smaller units stationed on the Potomac River and at Crisfield. The state Department of Natural Resources hydrographic unit based on Kent Island is responsible for speed limit and hazard signs, smaller orange-and-white buoys and markers that warn of environmentally sensitive areas.
On a recent steamy day, Baltimore's ANTs set off from Curtis Bay for Back River to check on what the maritime community calls a "red nun" buoy, a conical-shaped marker on the right edge of the channel that boaters should pass on the left. (A "green can" buoy marks the left-channel edge.)
"You never know what you're going to pull up," said Senior Petty Officer Chris Beahr, a lanky man with an easy smile who commands the boat. "Trees, anchors. We've pulled up a whole tackle shop of lures and fishing gear."
And the team never knows until it gets there what is causing a buoy to malfunction. It might be bullet holes from a vandal's gun or an osprey nest covering a solar panel.
"In the last three months, ANT Baltimore has had three aids destroyed because they were hit by boats," Beahr said.
The most spectacular crash, he said, involved a buoy off Kent Island that was struck so hard, a 25-foot section of stainless-steel handrail was jammed into the buoy 10 feet above the waterline.
"It wasn't reported," he said, shrugging. "It didn't do much of anything to the light, but it did plenty of damage to the boat."
Boatswain's Mate 1 Michael Maiocco points the bow toward the Key Bridge. The vessel is a pug-nosed, 49-foot Buoy Utility Stern Loading boat — called Busl — built in 2001 at the Curtis Bay Coast Guard Yard.
It's just 19 miles to Back River Buoy No. 2, located near Hart-Miller Island. But getting there will take a big chunk of the morning. Busl's top speed is 10 knots, or 11.5 mph.
The lack of speed is a running joke on board. When Maiocco goes to full throttle, members of the crew lean backward as if on a cigarette boat and laugh.
The Busl compensates for its lack of get-up-and-go with the muscle power to haul 2.25 water-logged tons onto the deck for inspection.
A red binder contains all the maintenance paperwork on Buoy No. 2 back to the early 1990s. The marker is known to drift a bit off its station — 35 yards last year. And something is causing the chain that anchors the buoy to the bottom — 30 feet long and as thick as a man's wrist — to wear too quickly.
All of the information also is logged into the ANT computer, which helps track the intervals between service calls. That work flow can be rearranged when bay pilots and boaters report something amiss.
"We rely on them a lot," Beahr said. "When an aid is reported as not working as advertised, we determine how severe the discrepancy is and respond anywhere between immediately and within 30 days."
On the way to Back River, crew members check other markers with binoculars and make notes.
Buoy No. 2 takes less than an hour to lift onto the deck, clean and inspect. The chain is still chafing, so ANT will continue to check on it while looking for remedies. By noon, No. 2 is back in the water, and the Busl has turned for home.
But off North Point State Park, a crew member notices that a range light marking an approach to the Patapsco River is out. There's a groan. It wasn't that long ago that the team replaced the underwater cable powering the light after it was run over by a recreational boater.
Maiocco reaches for his phone and calls in the work order.
One day is ending, but the next day's work already is taking shape.