BRANSON, Mo. — At first, the water splashing into the boat was comforting, a cool-down on a hot day.

But then came a massive swell that rocked the boat, and Tia Coleman started getting nervous. Before she knew it, another wave tore through, the boat sank and she could not see or feel anything. Not the son who had been sitting next to her, not her other two children, not any of the 10 family members who had joined her on an amphibious tourist bus — or duck boat — on Thursday afternoon.

“Lord, please let me get to my babies,” she prayed at one point, recalling the ordeal at a news conference on Saturday.

“If they don’t make it, Lord, take me, too,” she thought at another.

As it turned out, Ms. Coleman, 34, and her 13-year-old nephew, Donovan, were the only members of the Coleman family to survive one of the deadliest duck boat accidents in the country’s history.