The Nova Scotia native faced his fears on Sunday when he swam alongside 31 other people from New Brunswick to Prince Edward Island for the third annual Big Swim charity fundraiser in support of people living with chronic illness and disease.
"Unbelievable," said McDonald, after completing the 14-kilometre swim along the Confederation Bridge in under five hours.
"Just blessed — an incredible, incredible day. Perfect weather for the third year in a row."
The 2013 swim raised more than $130,000, which is almost evenly split between Cystic Fibrosis Canada and Brigadoon Village, a recreational camp in Nova Scotia for children living with a chronic illness, a condition or a special need in Atlantic Canada.
Supporting access to summer camp was part of what inspired one young Nova Scotian to take part in the swim.
"I love going to camp," said 15-year-old Jessica Plummer from Hammonds Plains, N.S. "It's like my favourite thing — it's so much fun and all my friends go."
She says she thinks it is unfair that a chronic illness would stop anyone from being able to attend summer camp.
Plummer set a record on Sunday when she became the youngest female to cross the Northumberland Strait, adding that the final kilometre-and-a-half was "probably the hardest thing I've ever done."
She beat a 2004 record for youngest female swimmer set by 16-year-old Melanie Leger, according to the online database Maritime Open-Water Swims.
The record for the youngest person to ever swim the Strait goes to 14-year-old Ralph Brooks in 1964.
"It was so cool when I got to the beach and all my family was cheering for me and all the people on the beach were clapping," said Plummer. "It was such a great experience ... a once in a lifetime feeling."
The Big Swim 2013 set a second record, for the largest group to swim the Strait together.
McDonald, who co-founded the event in 2011, said in the initial swim he and two others made the crossing. The following year the number of swimmers jumped to nine.
"I think when we sat down at the beginning of (this) year and said let's do this again we thought if we were lucky we'd get 10 or 15 again," he said.
To have so many participants this year is mind-boggling, he added.
The first swimmer to complete the crossing was Steuart Martens, who came from Washington, D.C., to participate in the event.
"It was pretty spectacular," said Martens. "Beautiful scenery — the bridge was gorgeous."
McDonald said finishing this year's event put him at a loss for words.
"I'm standing here looking at 300 people on the shore and all the volunteers and all the work they did and kind of humbled by it all," he said immediately after completing the crossing.
"One of our principles is achieving something that you think is extraordinary at the beginning but that you end up accomplishing."
- By Geordon Omand in Halifax