"We waved and we splashed. We waved and we splashed. We waved and we splashed," Lanny said. "And we get nothing."

They treaded water for an hour before Lanny decided they needed to head to shore, which he could see only from the peaks of the highest waves.

As Mary swam, she continued to veer off course. Lanny, exhausted by righting her path, instructed her to float on her back. He pushed his mother by her legs, as if her head were the bow of a boat, chopping through the waves.

The pushing went on for an hour, as Lanny tried to get them closer to the coast. That's when Mary told him to hold her hand.

He told her he couldn't tread water next to her and still make progress toward shore. But with greater urgency, Mary began pleading with him.

Then he lied — saying that he could see nearby houses, getting bigger by the minute.

His mother kicked her legs, and Lanny took two strokes and went back to push her again. Her legs were limp.

Mary was dead.

Fatigue sets in

Back in Fort Washington, Allison began to wonder why Lanny and Mary had not returned. She knew Lanny did not fly in the dark; the plane had no landing lights. Allison tried to get through to the Federal Aviation Administration.

"The FAA told us to call Lockheed [Martin, which tracks flight plans]. … Lockheed told me at that time that they had lost contact with him and that they'd contacted search-and-rescue. That's when it really hit me," Allison said.

Lanny had left his mother behind, to float away in the wake. He described the decision to leave her battered body as "cold and calculating." But he reasoned that his mother would have wanted Lanny to save himself, not worry about her lifeless body.

As the sun went down, Lanny's back hurt and he was shivering, but he continued to push through the waves. By 6 p.m., he reached a narrow sandbar where he could touch bottom. His spirits lifted and he continued to move toward land.

Lanny was getting close. He could finally see lights on the shore.

But a marsh and a bay, called Shanks Creek, still separated him from the twinkling lights of Smith Island's Rhodes Point.

The hour spent crawling through the bog was the most physically demanding part of the journey, Lanny said, and his body began to falter. Lean and strong, he had been on a fitness kick during the 10 weeks leading up to the crash and thinks it improved his chances of survival.

"I knew I wouldn't drown, but I was in and out and in and out of the water with the wind and the sticky, stinking mud, crawling on my hands and knees, fighting fatigue and hypothermia," he said.

He focused on a bright, yellow glow at one home. He could see lights through a window.

"I guess it was about 8 o'clock, I'm starting to watch a ball game, a football game, and I heard somebody come to my door bang and yell, 'Help me. Help me,'" said William "Max" Cline.

Cline was not entirely surprised to see Lanny, dripping at the door. He'd seen and heard the search helicopters going back and forth all evening.