“All hands man your battle stations. Enemy aircraft spotted off the port beam."

An alarm sounds, followed by the words no Navy sailor wants to hear.

“Missiles inbound, headed for port side. All hands brace for shock."

The sound of one explosion, then another, fills the air.

“Hit Alpha ... Hit Bravo," the intercom announces. “Investigators away."

The men and women on the ship's deck leap into action. Several go below to check for damage. They find water spewing into the compartment from several spots, including a lightning bolt-shaped gash in the hull. The water is quickly rising to their chests.

Something must be done.

It's the sixth week at Officer Candidate School for Class 05-08. Today's lesson: If you're a Navy officer, you better have some idea how to save your ship from sinking. The instruction takes place inside a building resembling a warehouse, where a nearly life-sized mockup of a ship is partly submerged inside a pool.

Life at OCS continues to be full of physical training, marching practice and rifle handling, which will be on display at graduation ceremonies. But the class has now entered a phase where learning is front and center. The students spend hours every day sitting in classes and studying at night in their rooms.

But damage control — including extinguishing fires and plugging leaks — is best taught hands-on amid dancing flames and spouting water.

THE AIR IS WARM and humid when the students enter Building 403, built around the 38-ton, 48-foot long mockup of a Navy ship immersed in a 37,000-gallon pool.

It's named the Wet Trainer, but is affectionately called Buttercup. The story behind the nickname is that a ship sprung a leak when an admiral was on board. His yappy dog, Buttercup, supposedly woke a crew member who then noticed the dangerous leak. Because it took the crew hours to repair it, the admiral returned ashore determined to build an onshore facility where sailors could train for emergencies. The part of the story that isn't true is that the sailors plugged the leak with poor little Buttercup. The students, wearing blue shorts and white T-shirts, don rubber boots with steel toes and white safety helmets (blue ones to alert staff that they're not very comfortable in the water). They gather for a demonstration on stopping leaks. Because the ship's deck is 8 feet high, the students at the edge of the pool must climb steel steps to get aboard. They gather around Damage Controlman First Class Michael Cajigas, who is standing on deck next to a hatch that leads to one of the compartments below.

“Odds are, you are going to find some damage down there," he says. “Everybody ready to get wet?"

After the announcement of the missile strike, the students break into groups and perform assigned tasks. Some assess damage. Some retrieve tools from a repair locker. Some relay communications to the team leader. The goal is to repair a leak in the ship's de-watering system, which will allow the water in the flooded compartment to be pumped out.

Between the sounds of water spewing into the compartment and the pump engines grinding away, the students must shout to be heard. Wooden beams they use for buttressing float around in the flooded compartment.

Matthew Gottschalk must dive underwater and hold his breath for as long as he can while tightening the thread of a flat patch to secure it over a hole in the flooring. He resurfaces and dives again to finish the job.

In a second exercise, the ship lists sharply to port, catching the students by surprise. Then Cajigas tries to rattle them further, announcing, “The on-scene leader is dead. What happens now?"

Since the attack on the guided missile destroyer Cole, where many crew members were killed, death has been introduced into drills, Damage Controlman First Class David Varela explains.

At lunch afterward, Officer Candidate Lenora DeRoy, who seemed a bit apprehensive as the team leader, talks about the experience.

“At first I wasn't sure what my responsibilities were. It was a bit overwhelming. I could have been louder and more commanding," she says. “When I was informed I had died, I said, ‘Did I do something wrong?' They said no. It was a good experience and a good eye-opener."

IN LESS THAN 24 hours, the students go from plugging leaks to fighting fires.

They arrive at a complex of buildings off the Navy base and file into a hallway. Hanging on walls are framed black-and-white photographs of naval disasters, many of them depicting the aftermath of horrific explosions — raging fires, gruesome injuries, dead bodies.

After a couple of hours of classroom instruction, they put on tan fire suits, gloves and green boots. They each pick up a fireproof woven hood, a helmet and an oxygen tank and head to the Fire Trainer, a windowless, multistory building, where simulated fires are fed by a large outdoor propane tank.

Inside, they sit down on a cement floor next to a wall-length pane of shatterproof glass. They are about to find out just how wild a “wild hose" can get. A water valve is turned and almost instantly, on the other side of the glass, a hose with a nozzle rises from the floor like a python snake and begins swirling around violently. The valve is turned off and the hose falls harmlessly to the floor.

Outside, the students are shown how to control a wild hose by using what looks like an oversized pair of pliers to crimp the line.

Next, the students get detailed instruction using their breathing apparatus. They put tanks on their backs and masks over their faces. Now it's time to fight fires.

One of the instructors stands outside a metal door, the entranceway to the mockup of a ship's interior.

“Cool to the touch," he announces and opens it slowly. “Advance all lines!"

The students carry two 1½-inch hoses into a dark room where fire has erupted from a fake oil shaft. Virtually the only light emanates from the flames themselves. White non-toxic smoke fills the room to reduce visibility. The students have been told to hit a lit panic button if they feel claustrophobic. None do.

The students take turns holding the hose and aiming the nozzle. In each room, a staff member remotely turns down the propane to simulate the fire being extinguished. The water has no real effect on the flames. The most dramatic fire appears to consume a torpedo, which the students are careful to avoid hitting directly with the water stream. Flames shoot up to the ceiling and warm the entire room.

“It can get really hot," says Damage Controlman First Class Shimran Ali, estimating the temperature to be 280 to 300 degrees. “It's the real deal."

THE SCENE is far less dramatic several weeks later in a classroom back on base.

The students take just one course at a time. The first course, Naval History, is an online offering they complete at OCS or before they arrive. The course Division Officers teaches them basic administrative duties. In Engineering, they learn about turbine engines, steam plants and ship design. They study plotting and relative motion in Maneuvering Boards. And in Naval Warfare, they learn about military strategy and different types of ships and weapons.

“It's not difficult information," says Nicole Lobecker, but “it's very fast paced."

She failed Naval Warfare the first exam, scoring less than the required 80, but retook it and got a 96. Since then, she's scored in the 90s in all her other courses.

Today's class is Navigation, which is the last course and considered to be the hardest. And tomorrow is the final day.

Navigation won't be an essential skill for students who will become supply officers or intelligence specialists. But for those destined to become surface warfare officers, it will be vital.

Among those who will be “driving ships" are Lobecker, Adam Cole, and Jason Moehlmann, all of whom joined Class 06-08 after failures forced them out of Class 05-08. Moehlmann and Cole, who flunked two inspections, finally passed with their new class. Today, they and their classmates are seated at long tabletops in the stadium-style seating lecture hall. In front of them are charts of Narragansett Bay.