Athletics Canada has confirmed that Daundre Barnaby died at a training camp in Saints Kitts yesterday afternoon.
The 24-year-old 400m runner, who competed for his country at London 2012, is said to have disappeared while swimming with some of his teammates in the ocean and he was later found to have drowned.
"This is such a sad and profound loss. Daundre was an outstanding athlete and an even better young man," Athletics Canada chief executive Rob Guy said in a statement.
Barnaby also featured at last year's Commonwealth Games in Glasgow.