Shortwave marine weather forecasts are broadcast in numeric mafor codes.
Marine forecast codes are explained or decoded by the following references.

Listed in order of usefulness, but one should look at them all for the best understanding of Mafor code use in Canada
Pat's Boating Mafor Code
Dean's Sport & Dive How to understand Mafor code
Pro Bass Fishing What is the Mafor code?
Environment Canada marine weather services Mafor decode table

Take with you a printout of one of the above to help you decode weather radio broadcasts of the Mafor codes.

One can enter the codes into the MAFOR (android or iOS) app to unwrap the forecast.
Regardless, always take a paper based decoder large/remote waters.

Ontario text forecasts includes links to marine, mafor & wave height forecasts