The Canada Day long weekend proved to be deadly in Ontario as five people drowned and two others are presumed to have drowned during the holiday.

The combination of an extended weekend and sweltering heat sent thousands of people into swimming pools, lakes and rivers to cool off and have fun, but things took a tragic turn in several communities.

One of the deaths occurred at a popular swimming spot on the Welland River in Niagara Falls on Sunday night.

Cheryl Bradbury, who was swimming in the river, said she tried to save a 27-year-old Toronto-area man as the current carried him downstream and he began struggling to stay afloat.

“I tried to go over and swim and save him but when I got there it was too late and the current was too strong, so he went right under,” Bradbury said.

The man’s body was recovered from the water a short time later, Niagara Regional Police said.

His name has not been released.

This was the second incident to occur in Niagara Region in less than 24 hours.

Early Sunday morning, a 19-year-old St. Catharines man disappeared after he fell into Twelve Mile Creek in Port Dalhousie.

Police said the man was with friends when he fell into the water at the crest of a hydro weir's waterfall. Police continue to search for the man, who is presumed drowned.

In Peterborough, police divers recovered the body of an Oshawa man who drowned in Little Lake on Sunday afternoon.

Police said the man, identified as 30-year-old Charles Urqhart, slipped below the lake’s surface while swimming near the Peterborough Art Gallery.

Meanwhile, police divers have recovered one body and continue to search for a second after two men, aged 21 and 26, disappeared in the Ottawa River in Ottawa on Saturday.

A passerby tried to save the men but had to swim back to shore after the rescue attempt put him at risk.

Police say alcohol may have been a factor.

In two other incidents this weekend, a 27-year-old man drowned at a beach in Grand Bend on Sunday night, while a 79-year-old man drowned while swimming in Lake Huron at Saugeen Shores.

With files from CTV Toronto and The Canadian Press