US Visitors to Canada
The Canadian Government has opened the Border as of August 9 to US citizens who are fully-vaccinated using one of the 4 approved COVID-19 vaccines used in Canada. These are Pfizer-BioNTech; Moderna; Janssen (J&J); AstraZeneca.
The detailed announcement can be seen here. Another one issued later from the CBSA can be seen here:
Competitors wishing to cross the Border to attend the M242 Canadian Championships need to set up an account with, and fill in the, ArriveCAN website or App, which can be found here, per the Canadian Government announcement which says:
"Subject to limited exceptions, all travelers must use ArriveCAN (app or web portal) to submit their travel information. If they are eligible to enter Canada and meet specific criteria, fully vaccinated travelers will not have to quarantine upon arrival in Canada."

Proof of a negative Covid-19 test is also a requirement, and must be administered during the three days before arrival in Canada. Canada generally accepts molecular Covid-19 tests, which look for the virus’s genetic material, such as polymerase chain-reaction tests. It doesn’t accept antigen tests, which look for viral proteins

Reporting requirements for private boaters
Boaters can clear via phone at (toll-free) 1-888-226-7277 or at one of the small vessel reporting sites, as follows (which include the Port of Sidney, Oak Bay Marina, and Canoe Cove in BC):