SOUTH THOMASTON — As one would expect from a Navy man, the message on Capt. George Kittredge’s answering machine is Morse-code blunt: Tuesday. Out on the water, giving submarine lesson. Back by 3:30.

Aye-aye, skipper, except it’s actually Monday.

“Hey, give an old sailor a break,” he says, explaining the time warp while leaping from his K-350 one-man sub to the South Thomaston dock. “When you get to be 78, you’ve got to keep moving. I don’t really care what day it is as long as I don’t see my name on the obituary page.”

Kittredge keeps moving by building submarines — 42 one- and two-man models since he retired from the Navy in 1962 after commanding his own full-sized version in combat during World War II.

The subs (K for Kittredge, followed by a number — 250, 350 or 600 — the depth in feet to which they’ve been tested) are used worldwide for underwater research and salvage operations, the only such boats certified by the world’s three leading marine engineering associations.

They’re also used for fun — like the one a wealthy Georgian bought so he could watch the fish he stocked in the lake he built.

“Once you go down, you’re hooked,” he said. “It’s so quiet down there, so fascinating. I knew this was what I wanted to do the first time I saw one.”

That first time was on the deck of a heavy cruiser in the Pacific, Kittredge’s first assignment as a young Naval Academy graduate.

“It was right after the battle of Coral Sea. We were in Sydney, when four Japanese minisubs snuck into the harbor. I manned a gun — we were giving it to them pretty good — and I kept thinking they were so slow and unmaneuverable. I knew I could do it better.”

He did, but he had to learn the perils of the business world first.

“I was just out of the Navy and I went into a bank to borrow $10,000 to get started. When I told the bank president I wanted the money to build submarines, I thought he was going to call the security guard, so I had to do it on my own, using my extravagant military pension, scrounging and salvaging.”

The scrounging goes on at Kittredge’s cockeyed shop on the Weskeag River, with the subs tested and launched from the salvaged Epsilon, a black steel catamaran barge that’s as ugly as it is functional. Kittredge has one full-time helper — Don Bixby — auto mechanic turned sub builder, with Tom Kealin, a retired Air Force electronics whiz, lending a hand in the summertime.

His first sub, a K-250, was sold for $3,500 to a Florida outfit doing shark research. Later models have gone for $30,000 to $150,000, depending upon the size, the strength of the hull and the level of “creature comforts” the buyer wants.

The subs are battery-powered, with an electric motor in the stern providing propulsion and serving as a rudder. Two smaller thruster motors, mounted on each side of the hull and able to rotate in a full circle, guide the sub up and down. Buoyancy is controlled by ballast tanks fore, aft and beneath, with air stored in scuba tanks. Breathing air in the hull is kept fresh by a carbon dioxide scrubber system — standard equipment. There’s plenty of portholes for visibility and the subs come in any color, as long as it’s yellow.

They’re also loaded with safety features, including, as a last resort, a detachable lead keel that can be jettisoned for emergency surfacing. There’s never been an accident in a Kittredge sub, except the time a leaking scuba tank blew the hatch open, shooting Kittredge to the surface in a bubble of air.

Well, there was one other accident. “I had a sub on a trailer and was backing it down to the shop when the hitch broke,” Kittredge said. “The sub and trailer crashed through the shop wall, leaving a good-sized hole. Imagine my surprise when I found out my insurance didn’t cover damage to a building by a submarine.”

This day’s submarine lesson is being taken by Wayne Peabody of Newbury, Mass., the K-350’s new owner. Peabody, a pilot and diver, plans to use the boat in his business, Sub-Sensor Technologies, for underwater mapping, salvage, research and maybe some treasure hunting.

Peabody also is a classical guitarist who has studied with the great Christopher Parkening. “I believe in going to the top when you want knowledge,” Peabody said during a break from his instruction. “If you want to learn to play a Bach prelude, go to Parkening. If you want to learn about submarines, go to George Kittredge. He’s the master. He’s devoted his life to this.”

Peabody says the experience of driving a Kittredge sub “is awesome, in the truest sense. You just slip under water and there you are, 50 feet down, in total silence, wearing a T-shirt and shorts, watching the fish swim by. It’s a different world. I feel like Alan Shepard in his Mercury capsule, except this is inner space instead of outer space.”

Peabody’s final exam is interrupted when one of the thruster motors conks out. The sub, which he plans to christen Xoc (the Mayan word from which our “shark” is derived) is hauled back onto the Epsilon. Kittredge, Bixby and Kealin take the cranky motor apart, fix it and put it back together while Peabody paces — not worried about the wisdom of his investment, but about how soon he’ll get it back in the water.

The motor’s fixed and the new owner is back inside, raring to go. “He reminds me of a guy in Hong Kong I sold a boat to,” Kittredge says. “He sent me a telex the day he launched it: `Great news! I took my first cruise in Hong Kong harbor today. When I surfaced, all the TV cameras were there, a huge crowd was cheering. It was great! P.S. — what do I do when the batteries start to smoke?’ ”

A rope is cut, the Xoc slides off the back of the barge, hits the water with a tremendous splash and is gone. Us topsiders eat lunch — sandwiches (submarine, of course) and oatmeal cookies — while Peabody cruises, too busy enjoying the scenery to use the radio.

Just when we’re all starting to wonder where he’s at, Peabody surfaces, coming really, really close to sticking his conning tower through the hull of a moored sailboat that looks to be quite expensive.

“Boy, that’d be one to explain to the insurance company,” Kittredge says. “Actually, he’s doing real well. He just needs to relax more, stop fighting the controls. He’ll be fine.”

Except for one K-350 Kittredge is keeping for himself, the Xoc might be the last of its line, but that doesn’t mean the captain’s hanging it up.

“My next project is a pedal-powered sub. It’s going to be the exercise rage of the 21st century. Can you imagine going down to 250 feet and pedaling your way back to the surface? That would get your heart rate going. It’s going to work. We have to get a little more propulsion out of it, but it will work.”

So, can you make any money building miniature submarines? “Sure you can, almost as much as it costs to make them. I’ve retired four times now, but I always come back when I find myself sitting still for too long. Put a little money in my hands, and you know I’ll spend it building a submarine.”

Which brings Kittredge to the project he’s had on the drawing board for years, a dream that needs only an associate with deep pockets to come true.

“It’s a 30- to 40-foot sub for the family, like an underwater RV. Think of it — camping on the ocean floor, watching the fish swim by like you watch television. I know how to build it. I just need a person with a lot of money and a sense of adventure. Let me know if you find such a person, okay?”

Aye-aye, skipper.