I toured the USS Cobia, a World War II submarine that sank 13 ships and received 4 battle stars. Take a look inside.

The USS Cobia is exhibited at the Wisconsin Maritime Museum in Manitowoc.

In 1970, the USS Cobia was turned into a memorial for submariners in Manitowoc, Wisconsin, a town known for the Manitowoc Shipbuilding Company, which built 28 submarines during World War II.

In 1986, the USS Cobia was designated as a National Historic Landmark, added to the National Register of Historic Places, and permanently docked for exhibition at the Wisconsin Maritime Museum.

General admission to the museum costs $22. Veterans pay $17, and active military service members receive free admission.

Tickets can be purchased on the Wisconsin Maritime Museum's website.

My tour guide, Mark Becker, served on a US Navy submarine during the Cold War.

Becker worked as a cook on the submarine USS Silversides.

The museum also offers self-guided audio tours through an app, but I was excited to walk through the vessel with someone who had experience living and working on a submarine.

The USS Cobia measures 312 feet long, nearly the length of a football field.

The front and middle of the deck were made of teak wood, which the Navy frequently used on submarines because it doesn't rot and doesn't float. If a piece of wood broke off, it wouldn't float to the surface and give away a submarine's position.

The back of the deck was made of steel since it was above the engines, which ran at high temperatures.

At the base of its periscope, an upside-down broom indicated that the submarine sank an enemy ship, a Navy symbol still in use today.

"Any US Navy ship that is flying that broom has made a clean sweep of the enemy from the sea. So in other words, they sunk an enemy ship," Becker said.

Becker indicated patched holes on the top of the submarine that were caused by enemy fire.

While bullets would bounce off the submarine, heavier artillery could punch holes in its surface.

A plaque on the deck paid tribute to Ralph Clark Huston Jr., a 19-year-old crew member who died in battle.

Huston Jr. was fatally wounded in a firefight with Japanese warships in 1945 and buried at sea. He was the only USS Cobia crew member who died during the submarine's six war patrols.

The first stop on the tour inside the submarine was the forward torpedo room.

Torpedomen, crew members who were in charge of loading and firing the torpedoes, slept in the room on pull-out bunks.

Each torpedo weighed over 3,000 pounds.

Metal poles on either side of the door were part of the USS Cobia's sonar system.

Sonar, an acronym for "sound navigation and ranging," uses sound pulses to detect and measure distances to targets.

We proceeded through the hatch to a narrow hallway leading to the officers' quarters.

Each section of the submarine could be sealed off from the others with watertight doors.

In the officers' pantry, food from the galley was reheated and plated on fancier dinnerware for higher-ranking crew members.

Officers ate the same meals as the rest of the crew.

Officers ate, held meetings, and spent their free time in the ward room.

The room was laid out like a restaurant booth, with benches on either side and a table in the middle. Food was served through a window connecting the ward room to the officers' pantry.

The executive officer, who was second-in-command under the captain, shared a room with two other officers.

The more bunks in the room, the lower the officer's rank.

Another room featured bunks for four officers.

The room included a small pull-out bench and folding table and a closet to hang uniforms.

Chief petty officers slept in a room known as the "goat locker."

According to the Naval History and Heritage Command, the nickname dates back to 1893, when the officers' rank was established. Chief petty officers were in charge of the goats kept on ships to produce milk, and the animals were kept in their quarters.

Becker offered an alternative colloquial explanation.

"By the time a man makes a chief petty officer, he's been in the Navy for a while — at minimum 10, 15 years," he said. "So they called this the goat locker, as in, old goats."

Only the captain enjoyed the privilege of a private stateroom with a phone that could call any room on the submarine.

The photo on the desk showed the USS Cobia's actual captain, Captain Albert Becker, who earned the Navy Cross and Silver Star Medal for his five war patrols with the submarine.

The yeoman served as the submarine's secretary in a small office called the yeoman's shack.

The yeoman handled all of the submarine's paperwork, including crew personnel records and order forms for food and mechanical parts.

The control room acted as the brain of the submarine with crucial equipment that controlled and measured the ship's direction and function.

The control room was staffed around the clock.

The brass steering wheel in the control room functioned as the backup steering wheel, known as the auxiliary helm.

The main helm, or steering wheel, was located in the captain's conning tower located above the control room.

"Everything on a submarine has a backup," Becker said.

Other wheels in the room controlled the submarine's depth by moving bow and stern dive planes.

Dive planes acted like the fins of a whale, shifting the submarine's angle while diving or surfacing.

The nickname "bubbleheads" for submarine sailors comes from this tool in the control room, an inclinometer.

The inclinometer functioned like a carpenter's level, using a bubble to measure the submarine's tilt and slope.

The USS Cobia's radio room still works thanks to the Wisconsin Maritime Museum's restoration efforts.

Becker said that the submarine's SJ-1 radar is the oldest operational radar in the US.

"Not that I'm bragging, but we have the most awesome volunteers who come and work on the Cobia just because they love her," he said. "Those are 80-something-year-old radios with the big old tubes in them and stuff. These men will go to junk stores and scrap places and look for tubes."

The radar is so powerful that Becker said it can interfere with phone service in the surrounding town when it's turned on, which can elicit "nasty notes from the phone company" telling them to "turn that thing off."

The submarine's small kitchen fed its 80 crew members three meals plus a midnight snack every day.

Becker, a former submarine cook, said that food was key to the crew's morale, especially on holidays like Christmas when service members often felt homesick.

"When they catch a whiff of turkey or ham or cakes baking or anything like that, they catch that smell, it'll pop them out of it like that," he said.

The crew's mess was a multipurpose room where sailors ate meals, watched movies, read books, and took classes.

Crew members ate in shifts since the room could only seat 24 people at a time.

The crew's quarters had 36 bunks, which wasn't enough for each person to have their own designated bed.

Using a system called "hot racking," crew members shared bunks by rotating their use with people assigned to different shifts.

Each crew member was allotted one cubic foot of space for their personal items.

The crew's washroom featured two showers, four sinks, and two toilets for 72 people.

Showers were rare for sailors on the USS Cobia due to the submarine's limited supply of fresh water. Crew members could use one sinkful's worth of fresh water per day.

Using the bathroom on the USS Cobia was not a simple task — it took nine steps to flush the toilet correctly.

If the procedure was not properly followed, the contents would shoot back out, leading crew members to nickname the toilets "freckle-makers."

The USS Cobia had four 16-cylinder diesel locomotive engines, two in the forward engine room and two in the after engine room.

The two engines in the forward engine room still work.

With all of the heat from the engines trapped inside the submarine's steel frame, the average temperature on board was 90 degrees Fahrenheit. Most crew members wore cutoffs and sandals instead of uniforms.

The diesel engines charged the submarine's battery banks, which powered its electric motors.

The water purifying system in the forward engine room could produce up to 1,000 gallons of fresh water each day.

Most of the freshwater supply went toward maintenance, not hygiene. The submarine's batteries required fresh water since they ran so hot that they evaporated their electrolyte fluid.

In the maneuvering room, crew members monitored the USS Cobia's electricity use and speed.

The USS Cobia could only charge its batteries while surfaced, so it usually moved slowly, around 2 to 3 miles per hour, to conserve battery power. Its maximum speed was 9 knots, or about 10 miles per hour.

"The faster we go underwater, the quicker the batteries are going to be depleted," Becker said. "Then you got to surface that much sooner."

The last stop was the after torpedo room in the back of the submarine.

During World War II, submarines had two torpedo rooms, one in the front and one in the back, so that torpedoes could be fired offensively and defensively, Becker said.

The torpedo launch tube featured an image of the cobia fish from the USS Cobia's battle flag.

Walt Disney Studios designed over 30 submarine battle flags featuring cartoon-like sea creatures during World War II. While Disney didn't draw the cobia depicted on the USS Cobia's flag, it was likely inspired by the studio's other designs.

I exited the USS Cobia in awe of its intricate systems and the service members who kept it running during World War II.

When I looked at my watch at the end of Becker's tour, I couldn't believe that nearly two hours had passed. The time flew by.

As I said goodbye and thanked him for the tour, I asked Becker about his favorite recipes from his service as a submarine cook. He said that the captain of the USS Silversides was a fan of his chocolate-chip cookies and once called the kitchen to ask for a plate when he smelled them baking.

"For the rest of the time he was on that boat, every morning when he woke up, there was a little plate of chocolate-chip cookies on his desk," Becker said. He pointed to his shoulder, indicating the spot where Navy uniform stripes indicate rank. "I got promoted."