Twenty-three people — including women and children — have been rescued after an ice shelf cracked and floated away in frigid waters of Ontario.

Fishermen Kevin Fox and Alfie How thought they were done for when they realised they had drifted to sea and their ice sheet was shrinking.

“I just started screaming: ‘The ice is opening. The ice is opening’,” How told The Owen Sound Sun Times.

“We just sat down as a group and said this could be the end.”

Ontario Provincial Police said officers responded to reports of several people stranded on ice near Balmy Beach, north of Owen Sound, about midday on Sunday (local time).

The ice shelf split into several sections and moved about two kilometres offshore.

Some of the victims trapped on the perilous block became partially submerged in the freezing water. Others running for an escape route plunged into holes in the ice.

“This became a life-threatening situation for several of the people due to hypothermia,” provincial police said.

Two helicopters were involved in the dramatic rescue, making multiple trips to pluck people off the shelf, starting with those most at risk.

Fishermen were trapped on an ice sheet. Photo: Kevin Fox

Fox told Canada’s Sun Times that the ice anglers had crossed some “good cracks” on their way to a fishing spot so they were “aware these cracks could open and were trying to keep an eye on them”.

They moved out to deeper waters in search of a bite, but that’s when the shelf separated. Fox realised they were moving only when he looked at his GPS.

As Fox’s group turned around to head back, the ice shelf broke again and one group began floating away from them as waves started to break the edges of the shelf.

“It was being eroded,” Fox said. “It kept getting smaller, and smaller.”

Fox wrote on Facebook that some started phoning their families.

“It’s something I will never forget — seeing grown men crying while saying goodbye to the people they love.”