As that a battleship headed your way, bristling with turreted guns? But wait. It’s no bigger than a war canoe, and there’s classical music — Wagner, in fact.

It all began when Bill Terra thought building a battleship might be an enjoyable hobby. He didn’t realize that his working model would consume years of his life and $10,000 in material. Labor? Don’t ask.

Now 71 and living in landlocked Levant, this former firefighter is owner-builder of the German World War II warship Graf Spee, a realistic scale replica powered by a concealed 15-horsepower outboard motor. Not bad for a vessel that weighs a ton when you add the stabilizing steel keel.

And the sound system that plays Wagner as Terra cruises about.

The story of this mini-vessel began some 35 years ago, when Terra built a six-inch plastic kit model of the Graf Spee, a “pocket battleship” that in real life was powered by eight diesel engines and gained fame — or infamy — in the 1939 battle of the River Plate off South America, where this Nazi raider was scuttled — just outside Uruguayan territorial waters — after being damaged in an encounter with the British.

Terra’s two-seater replica — sometimes his wife Caroline can be coaxed into crewing with him — nearly met a similar fate when smudge pots in Graf Spee’s stacks turned into blazing cauldrons. Alone on a lake and not wanting to lose his ship or have to swim ashore, he managed to douse the flames. “It could’ve been a disaster,” he said, but being a former New York City fireman, he knew what to do.

He retired from the fire squad in 1979 and for $3,000 bought 100 acres in West Levant, and he built a private airstrip beside his home. An Air Force veteran, he spent five years restoring an antique plane, and then considered building a six-foot radio-controlled model of the Graf Spee. But he thought bigger. As Terra said, “It was one of those eureka deals. The light bulb goes off and I said, wouldn’t it be neat to have one big enough to get in?”

Terra’s 30-foot Graf Spee, built from scratch, has 12 layers of fiberglass and a beam of 52 inches. “It’s still not complete and it probably never will be. I’m a perfectionist,” he said.

“It took me nearly three years to get it into the water. Every summer I take it out three or four times on different lakes. I went through a storm and she held up fine.”

Graf Spee didn’t get into a recent Rockland boat show, however, because the gatekeeper told Terra he would have to pay to display his boat. Terra turned around and towed his battleship home without so much as a parting shot.