If you are in Canadian waters I recommend either leaving the firearms at home or making sure your papers are in order. Canadian firearms laws are strict and punishment for weapons violations can get you incarcerated. Pistols of any sort and most black rifles are either restricted or prohibited. Restricted's require an Authorization to transport (ATT) from the Chief firearms officer of the province you are in, and likely a Restricted Possession and acquisition license (RPAL). You will not be allowed to be in possession of a pistol without a legitimate competition invite or the like. Prohibited firearms (which includes most popular carry pistols) can not be possessed under any circumstance by your average joe. Your average hunting rifle and shotgun are normally non restricted and you need a PAL to be in possession of them here. Long story short canuckistan is a legal cluster**** when it comes to firearms laws. Running afoul of those laws can result in some serious consequences ranging from a criminal record to a stay in the local prison. As a side note although us Canadians are very polite for the most part, you will notice most law enforcement are unaware of legalities around firearms and will assume you aren't allowed to have any guns in your possession. If you are determined to bring guns with you here is the people you will want to consult.
As a side note, if your route on the St. Laurence puts you anywhere near the native reserve (i think it's akwesasne mohawk to my recollection) your odds of being stopped and boarded are likely to increase 100 fold as it is a known smuggling area.