The 24-year-old from Victoria, who trains out of Vancouver, qualified by finishing 14th on the weekend at the fourth stop on the FINA Open Water Swimming World Cup.
Britain's Jack Burnell won the 10-kilometre race in Cozumel, Mexico, in one hour 42 minutes six seconds ahead of Esteban Enderica Salgado of Ecuador and Simone Ruffini of Italy. Weinberger finished in 1:42.20.
The competition doubled as a world championship qualifier for several countries.
Victoria's Eric Hedlin also qualified for the world championship as the second Canadian in the standings, finishing 29th.
American Haley Anderson won the women's event.
The top two Canadians were Jade Dusablon of Quebec City (27th) and U.S.-based Samantha Harding (39th). They also qualified for the world championships, scheduled for July 24 to Aug. 9 in Kazan, Russia.