For this small group of fit folks with sunglasses, beach season begins as it always does, a week before Memorial Day in a small bathroom at the 10th Street Medical Center. One by one, a woman in a floral blouse and blue latex gloves calls them in and hands them a sterile cup.

It’s the first day of the Ocean City Beach Patrol’s yearly Surf Rescue Academy, a week-long boot camp for newbie lifeguards. It starts, for rookies and veteran instructors alike, with a drug test. Call it their No. 1 priority.

“Yep, do it every year,” says Liz Vander Clute, 22, a newly promoted crew chief beginning her sixth season on the stand. “Now summer has begun.”

The beach is a place of satisfying sameness. Clockwork cycles are at the core of the shore, a comforting repetition of all that has come before and will come again: the ceaseless metronome of waves, the daily pulse of tides, the seasonal arrival of shorebirds, T-shirt vendors, sea breezes and tan lines.

Sea turtles lay their eggs at the same time and place every year. Families claim the same houses during the same summer week — and eat the same food. Pizza from Grotto on the first night, crabs from Hooper’s on the last.

And the lifeguards pee in a cup on their first day back.

“I’ve been doing this for 18 summers, and I still get excited on Day One,” says Dave Haight, a crew leader up on Condo Row. “I’m a total creature of routine.”

After the drug test, the guards drive back to Beach Patrol headquarters to be issued their “reds,” a big duffel of swimsuits, sweatshirts, T-shirts and hats emblazed with the life-ring crest of the OCBP.

They get an umbrella and a summer’s supply of SPF 35 from Panama Jack, a longtime sponsor of the 200-person squad. They get a whistle, but most will buy a better one, the state-of-the-art Fox 40 pealess. They already own shades, but most will acquire a pair of VonZippers, the professional choice.

And they get their buoy — a stout, plastic floatation device that looks like an oversize red rugby ball with handles. The buoy is to the lifeguard what the M16 is to the Marine, his constant companion, the tool he needs to do the job, which for the lifeguard can amount to more than 600 surf rescues a year.

The O.C. Beach Patrol, which has a national reputation for effectiveness, pulls between 2,000 and 4,000 distressed swimmers from the Atlantic each summer. They treat about 100 suspected neck and back injuries (the most serious from ill-advised dives into shallow water) and return about 1,000 lost children to about 2,000 hysterical parents.

“We have a 100 percent return rate on lost individuals,” says Sgt. Timmy Uebel, 48, a contractor and 28-year Beach Patrol veteran. “On the Fourth of July, the same person may be lost two or three times.”

The returning guards know to look for the umbrellas with the straightest ribs, the buoys with the longest lines.

“I’ve had everything in here for years,” says Haight, as he sorts through his duffel. He’s drilled his umbrella with bolt holes and wing nuts to keep it mounted, because he’s seen a beach patron impaled by a wind-blown umbrella.

He’s seen it all. Sometime in August, the 1978 graduate of Bethesda’s Walter Johnson High School will sit his 1,700th day on an O.C. lifeguard stand. That’s a record.

“Nobody’s got more time on the wood than me, man,” says the athletic 51-year-old former Marine, reading glasses and sunglasses both hanging from the collar of his Beach Patrol T-shirt.

There are 26 rookies in this training class. Another two dozen will fill a second course next month. All between 18 and 23, they start at $13 an hour, bumping to $14 when they clear a probationary period. Returning lifeguards earn an average of $15 and can clear $10,000 for the season.

The first official lifeguard shift won’t start until 10 a.m. on the Saturday of Memorial Day weekend. That leaves a few day of surfside training to break in, and wear out, the rookies.

They are already top physical specimens, having outswum and outrun more than 100 applicants for the job at two grueling beach tryouts last fall.

But they still have to master semaphore, the antique language of naval flag signals. They have to learn to spot the one flailing distressed swimmer amid the dozens of flailing safe ones. (Lifeguards are blatant profilers. If you are tanless, obviously out of shape, wearing street clothes or otherwise seem unfamiliar with ocean swimming, they will watch you like a hawk when you enter the water).

They will practice digging a toddler from a collapsed sand hole and stabilizing a broken neck in a pounding surf. They will learn to never, never turn their back on the ocean.

“Face east!” an instructor screams at a trainee who turns sidewise for a moment to answer a question from someone behind her. By the end of the first day, they walk backward and run backward, eyes locked on the waves.

“By the end of this week, they will never be able to relax on the beach again,” says Lt. Ward Kovacs, 50, a Lutheran pastor in his off time. Behind him, three rookies practice dragging 300-pound timber-frame lifeguard stands up the beach, still having “Face east!” screamed at them. “I can’t even walk by a puddle and not scan it.”

The “beans,” as recruits have been known since they were issued bright green rookie uniforms, will get on-the-job training and be on probation until they pass a series of competency tests. But by Monday, they’ll be in stands of their own, 200 yards from the next guard.

“We’ve had people have to do CPR on their first day,” says Jaime Falcon, 39, an economics professor at the University of Maryland Baltimore County and, now, the patrol sergeant in charge of rookie training. “They have to be ready.”

Falcon replicates as much of the lifeguard’s harrowing grind as he can. They run for miles in soft sand, swim the big surf until they crawl out, gasping, then run some more. The instructors are gleeful on the second day of training, when a tropical depression offshore kicks up a battering five-foot surf. No one is in the water except the guards.

“Get out there! They’re dying!” shouts Crew Chief Kelly McGrath, 26, as a group of recruits plunges into the heaving Atlantic for the fourth time. The five “drowning” swimmers are faking it, but the rip current they are in is real. One recruit, struggling to finish a 500-meter swim, has to be helped in by Uebel, who is patrolling on a surfboard.

“Turn around!” Haight yells as a monster wave looms above a returning rescuer. “Turn around! He’s gonna get . . . ouch. We haven’t taught them that yet.”

Falcon looks at his watch and frets about the classroom session they have planned with the bomb squad (every summer, lifeguards find forgotten fireworks and unexploded ordnance — including washed-up grenades — on the beach). But he decides to add another hour in the water.

“This is too good to miss,” Falcon says as dripping, wheezing “beans” lean on their knees around him, craning their necks to stay eye-locked on the water.

By the end of the week, most of the lifeguard stands that have filled the Beach Patrol parking lot all winter are distributed along the city’s 10 miles of beach. The faces of the recruits are beginning to show the “raccoon tan” around the eyes that will mark them as seasoned guards.

They’ve learned how to pull a panicked swimmer from the surf, and an injured swimmer. And a dead one.

Of the 10 surf fatalities in Ocean City waters in the past four years, not one occurred on the Beach Patrol’s watch, between the hours of 10 a.m. and 5:30 p.m., according to longtime Beach Patrol Capt. Butch Arbin.

But death by drowning is a beach ritual, too, and the training has included plenty of grisly war stories. Most of them started with rip currents and adults who go in to help struggling children. The very worst of them ended with two boys, 9 and 11, clinging to the body of their would-be rescuer — their mother.

“I’ve had some terrifying experiences,” says Haight, who has pulled off 17 rescues in a day. “But the only thing I’m really scared of is bringing in a dead kid. I see a kid in even a hint of trouble, I go” into the water.

For now, the shore is still nearly deserted, awaiting the holiday weekend onslaught. A troop of recruits runs by, kicking up sand on the empty beach. Haight sizes them up; they are a promising crop.

“On Day One, their eyes were like silver dollars,” he says with a laugh. “Today, they are like quarters. And by the end of the week, they will just be squinting, just looking for something in the water.”

“They’ll be ready,” he says. “I see it every year.”