The 80-year-old river pilot and sea captain extended his contract at Bath Iron Works to ensure he could pilot the 610-foot warship safely through three sea trials.

He said he couldn’t imagine retiring before the program was completed.

“I think I would’ve had tears in my eyes,” Walker said if he’d had to watch the ship head downriver from his nearby home instead of being at the helm.

The old salt is prized for seafaring abilities — and his knowledge of the Kennebec River.

The river’s tricky currents and twisting turns leave little margin for error when steering big warships coming and going from the shipyard. The $4.5 billion Zumwalt, bristling with high-tech gear and weighing in at 15,000 tons, cleared the river bottom with less than 2 feet to spare, he said.

“If it was easy, then anyone can do it,” he said matter-of-factly.

Walker’s official job title is port captain and he works under contract to serve as the skipper of Bath-built warships before they become Navy property. On Friday, the Navy officially took ownership of the Zumwalt, and sailors began moving aboard.

Over the years, Walker piloted frigates, destroyers, cruisers and container ships built at Bath.

In the olden days, white-knuckle moments came when ships were launched into the river for the first time with a splash. It was great fun for spectators but not for Walker, who oversaw tugs that ensured currents didn’t send ships crashing into a nearby bridge.

Those days are long gone. Modern warships at Bath Iron Works are built at a land-level transfer facility and floated in a dry dock with far less drama.

But the ships still have to travel down the Kennebec to reach open ocean, and they do so at high tide to ensure maximum clearance for the ships’ keels.

For the Zumwalt, care was required to ensure that the largest destroyer ever built for the U.S. Navy didn’t drift sideways, he said, and calculations had to be precise to ensure the sonar and propellers didn’t nick the river bottom.

Because the ship displaces more water when it moves, the 2 feet of underwater clearance at several locations on the river actually shrunk to only 12 to 18 inches, he said.

If that isn’t tricky enough, visibility was restricted. Because of the ship’s design, Walker couldn’t see the water directly alongside its sloping hull when docking and undocking.

He’s known for keeping his cool under such pressure.

“He never got frazzled about anything,” said Jeff Monroe, former Portland transportation director, who got to know Walker when he was a Portland harbor pilot. “You knew you were in good hands.”

With the ship being transferred to Navy ownership and his contract ending in July, Walker probably won’t be piloting any more Navy ships downriver.

The Zumwalt won’t be leaving Bath Iron Works again until September, when it departs for good to travel to Baltimore to be commissioned into service.

By then, the shipyard will have a new port captain, Mark Klopp. Still balking at retirement, Walker will stay on for another year as Klopp’s backup.

“It’s time for me to move on, as much as I hate,” said Walker, who’s been semiretired since 2001. “I really would prefer to work but time catches up with you. Let’s face it. Most guys would’ve quit when they were 65. I didn’t. It was only because I love the work. You hate to give it up.”