Rescuers search the Merrimack River for the body of a young man on Wednesday.

Search and rescue crews were called to the Merrimack River near the Hannah Duston Memorial site on Wednesday afternoon after a young man went underwater while swimming and didn’t resurface.

James Smith, a Hooksett resident who works in construction, said he and three coworkers stepped away from a job site to grab lunch and cool off in the river near Hannah Dustin Drive in Canterbury around 1:30 p.m.

Smith said he was the first one to jump in the water, followed by his coworkers.

One of them started struggling in the water and went under. Smith said he tried to pull the man to safety.

“I grabbed hold of his hand and was trying to pull him into shore,” Smith said. “I couldn’t and I came back.”

Witnesses at the scene reported that the man was submerged for nearly 50 minutes before rescuers finally found him near a sandbank and performed CPR.

The man was then transported to a nearby hospital. His current condition has not been released.

Officials remained on scene late Wednesday interviewing witnesses. No official statement was issued by press time.

After a series of drownings over the years, officials have warned about the dangers of the Merrimack River. Although currents look calm from the surface, they can be strong underneath, especially in areas with a quick drop-off.

Signs placed along the riverbanks in Canterbury included an illustration of a person on the water’s edge and the dangerous drop-off they could experience just feet from the shore.

Gopalakrishnan reports on mental health, casinos and solid waste, as well as the towns of Bow, Hopkinton and Dunbarton. She can be reached at sgopalakrishnan@cmonitor.com