LT. ANDREW Napoli spends most of his day riding up and down the city's rivers.
But it's no pleasure cruise - he's looking for threats to the safety of Penn's Landing and other waterfront properties.
Oh, and dead bodies.
"Spring is one of our busier seasons," Napoli, who leads the Police Department's Marine Unit, said during a recent patrol along the Delaware River.
"Because the water is so cold, the bodies don't decompose, and they sink to the river bottom.
"So in the spring, when the water warms, they start to surface. That's where we come in."
This spring has been eventful for the unit: Last month it pulled seven bodies out of the city's two major rivers within 2 1/2 weeks.
To hear Napoli tell it, that number is only "slightly above average."
"It's definitely tough at first, handling all those bodies," he said. "I don't want to say you get used to it, but you come to expect it; it's part of our job now."
And it's a tough job that often goes unnoticed despite the unit's record for protecting the waterways and saving people from themselves - they rescue an average of 50 people from the murky depths of the city's rivers and creeks each year.
"A lot of times, people joke about the Marine Unit and what a great job it is, and it is a great job," said Chief Inspector Joe Sullivan, who oversees the unit. "But when it's 'go' time, their work is serious business."
The Marine Unit, formed in 1859, is the longest-running specialized unit in the Police Department. It was originally formed to transport prisoners to riverside facilities and fight the piracy that threatened the young country's major ports.
These days, in addition to their routine patrols along the city's 90 miles of mappable waterways, the Marine Unit officers spend most of their time responding to reports of people threatening to jump into the rivers or scrambling to recover those who've already taken a plunge.
In either case, time is of the essence.
There's a small window of opportunity for the Marine Unit officers to recover a jumper, especially when they have to travel against the current from their headquarters at the U.S. Coast Guard base at Washington Avenue and Columbus Boulevard.
Even when the officers arrive at the location, they have their work cut out for them: The waters of the Schuylkill and Delaware are fast-moving and murky, making visibility almost zero for officers diving into them.
"Their job is dirty and intense," Sullivan said. "This isn't like Miami, where police divers are looking at crystal-clear waters."
A combination of abandoned cars, miscellaneous trash and who knows what else litters the bottoms of both rivers, making underwater travel treacherous. Add to that the soft nature of the soil on the riverbed, which kicks up mud and silt at the slightest touch, and officers are lucky if they can see their hands in front of them, Napoli said.
"Close your eyes: That's our visibility," he said. "Everything is by feel, which makes it so frustrating sometimes."
The bodies themselves rarely stay in the same spot, thanks to the strong currents rippling the two rivers. All of that makes rescues difficult, if not impossible, if police aren't nearby when the victim takes his or her dip.
That reality factors into another major part of the Marine Unit's job: persuading would-be swimmers to stay away from dangerous waters.
That includes the Wissahickon and other inland creeks and streams that run throughout the city.
"Kids go into them, they think it's cool and that they're safe," Napoli said. "It may look safe, it may look fun, but swimming there can kill you.
"And it's preventable."
Not everyone heeds that advice. Reports of kids struggling to stay afloat in those landlocked waters are inevitable every summer.
When those calls come, the Marine Unit has to scramble, sometimes searching the streams and creeks on foot because they are too narrow in some locations for boats to navigate.
Those creek-side rescues, carried out with minimal equipment, underscore the danger the unit faces and the skills they need to maintain.
"In swift waters, you have guys tied off to a rope; that's about it," Sullivan said. "As their boss, I have my heart in my mouth a lot watching them do that."
To ensure those rescues go off as smooth as possible, Marine Unit personnel train year-round, even in the winter.
In January, Napoli and his men took advantage of the frozen-over Schuylkill to practice diving into, and getting out of, icy waters.
"They have a lot of decisions to make very quickly, that's why they have to be the experts in their field," Sullivan said.
This is why rescue attempts from any body of water are best left to the professionals, according to Sullivan, who referenced the tragic story of Pete Luciano, the North Philly man who died last summer in an unsuccessful attempt to save his drowning son in the Wissahickon.
Becky Salmon agrees that amateurs should stay out of rough currents. She also admits how foolish she was to ignore that advice two months before Luciano's death, jumping into the creek's waters to save a boy struggling to stay afloat.
"You talk to anyone with experience with water rescue, and they'll tell you I'm an idiot," said Salmon, who works as an emergency medical technician in Montgomery County.
"I'm a strong swimmer, sure, but that's what everyone says."
Salmon said she acted without thinking when she saw that youth struggling to stay afloat while she was posing for engagement photos with her fiance on the creek's banks. Speaking from her years of experience responding to emergency situations, she has the utmost respect for the Marine Unit and their ilk, whom she says are "the real heroes."
"You tend not to think about them for a majority of the year," she said, "but when you're in a life-and-death situation, they're the ones who matter the most."