A boat that sank in the Chesapeake Bay had 23 people, including students, aboard. They all were safely rescued by a waterman. ( Maryland State Trooper 4/Courtesy of Maryland Natural Resources Police)

Jeremy Shockley heard the distress call come across the marine radio channel Wednesday as he and his son, Daniel, checked on their boat after catching crabs at a Chesapeake Bay marina on Maryland’s Eastern Shore.

“Mayday. Mayday,” Shockley heard over the radio about 5:30 p.m. “Vessel taking on water.”

He quickly surmised the coordinates and realized it was at Bloodsworth Island in Dorchester County, about 35 minutes north of his remote location in Wingate.

“I hollered, ‘Let’s go get them,’ ” Shockley, 42, of Toddsville, Md., recalled Thursday. He, his son and two friends took off to help rescue the boat’s passengers.

But they didn’t realize as they raced in Shockley’s 36-foot boat exactly who they were about to save — 14 fourth-graders, five parent chaperones and a teacher, as well as two instructors and a captain from the Chesapeake Bay Foundation who were leading the educational trip on the area’s ­ecology.

Jeremy Shockley, 42, of Toddsville, Md., helped rescue several people from a sinking boat in the Chesapeake Bay. (Courtesy of Daniel Shockley)

“No one said anything about it being kids or 20-plus people,” Shockley said. “We thought it was a fishing-party boat with two or three people.

“We wanted to assist them and help them get home,” he said. “I didn’t know what I was looking for.”

He and his crew arrived to find the youths and adults huddled in life jackets on top of the boat’s canopy, surrounded by 67-degree water half a mile from the ­shoreline.

“My heart went to my feet,” Shockley said. “When we got closer I realized there were 20-some people and there were 14 kids. . . . I just couldn’t imagine it. Seeing children sit on top of the boat like that.”

The custom 40-foot aluminum boat had hit a submerged object, leaving it punctured. The boat took on water and sank at least 8 feet, hitting the sand bottom.

“Some of them were shivering,” Shockley said, adding that the passengers were calm and quiet as he helped them safely board his boat. He wasn’t sure how to fit everyone he rescued, but he made room.

By the time local police and fire rescuers — along with the state’s natural resources police — had arrived, Shockely and his crew had safely rescued everyone.

“It is always hard to say what the outcome would have been,” said Candy Thomson, a spokeswoman with Maryland’s Natural Resources Police. “In a vessel with 14 children aboard that goes down in a remote area, that’s trouble. We were lucky in two respects — one, everybody was in life jackets, and two, that waterman was ­nearby.”

As Shockley took the children to the dock at Wingate, some emotional parents were waiting.

“Reality started sinking in when they got back,” he said. “It could have been a lot worse.”

No one suffered major injuries. The captain of the stricken boat, who has worked for the Chesapeake Bay Foundation for 10 years, was airlifted to a hospital and released. Others were treated for minor injuries and discharged.

At the time of the distress call, Shockley said he jumped into his boat and headed out without too much thought.

“I hope someone would do the same thing for me if I got in a jam,” he said.

Shockley prepared himself for the possibility of seeing a disaster as he arrived at the scene. He said the tide “runs hard” in that area and the children could have become separated if they had tried to get off the boat.

“They would have gone out in the ship channel and God only knows what would have happened,” he said.

Shockley also credited the captain of the boat, named the Karen N., for safely getting passengers on the canopy.

The Kent School said it has taken students on educational field trips for at least a decade with the Chesapeake Bay Foundation without incident.

The group in the sunken boat had been in the area on a trip and was involved in projects such as testing water quality; harvesting oysters, fish and crabs; looking at underwater grasses; and studying the ecology of the area.

It wasn’t known what the sunken boat hit, but local water users said it isn’t uncommon to find unexploded ordnance or other debris in the water near Bloodsworth Island, which was once a naval gunnery range.

The U.S. Coast Guard is conducting an investigation, officials said. The foundation said it plans to work with the Coast Guard to figure out how the accident happened, but it has no plans to cancel its educational programs using boats along the bay.

“They were calm and cooperative,” said William C. Baker, president of the Chesapeake Bay Foundation. “I’m so proud of students, staff and parents. They turned a bad situation into something as manageable as can be expected.”

Shockley described the people he rescued as“little kids trying to take a school trip and they wind up sitting on the bottom of the Chesapeake Bay.”

“It’s not a really good feeling,” he said. “It’s a feeling nobody wants to see. I was glad to see all eyes open.”