"Let's say you've got somebody from the local city who decides to beat the heat at the nearby Great Lakes beach because the local pool or water park is closed due to COVID," he said. "They're not used to that beach — they don't know what a red flag means in terms of a hazard. If there are other people already in the water, they are going to follow the guide of the people, not the flag.
"It was particularly young males who were at greatest risk. If you've got a bunch of young males who are escaping self-isolation, they are more prone to risk-taking, more prone to getting into the water and riskier behavior."
About 10 more young males drowned last year than expected from annual averages from the decade prior.
Though red-flag warnings existed for dangerous water conditions on Lake Michigan last June 6, no flag warnings were posted at the beach at Holland State Park. Christian Ngabo and Iain Rowe drowned in separate incidents that day.
Record-high water levels also meant shrunken beaches, Houser said.
"You start to spread people out," he said. "Even if you had a beach that had lifeguards at it, you now have people spread over a much greater distance, with less chance of an intervention."
Zeeland resident Greg Field Jr. is a water safety advocate and board member with the Homewood, Illinois-based Great Lakes Surf Rescue Project, a nonprofit organization that tracks and tries to eradicate Great Lakes drownings through training, public awareness and preparedness.
Field said he has yet to see the University of Windsor research.
"It's an interesting line of thought. ... Conceptually, it makes sense to me," he said.
Field is a transplant to Michigan from Florida's Atlantic Coast.