Boating in the ocean breaks one of my rules of life. "Never put my boat in water where there are fish bigger then my boat." I can see it now, large tenticles from a 90 foot Squid wrapping itself up and around my bridge of my 35 foot boat. For 18 years I boated on the St. Lawrence River. It runs from Lake Ontario to the Eisenhower Locks out to the Atlantic ocean and, in my opinion, is some of the best boating in the world. The down side is you only get about 6 months of boating.
Its commonly known as the Thousand Islands although there are actually about 1800 islands. The water is crystal clear and there are tons of coves to raft up with other boaters! There are many many towns to go to and going into Canada especially at Kingston is a great place to party. The Flora McDonald Confederation Basin has about 400 slips suitable for small craft and large yachts. There are many places to dine with all kinds of quisines and usually have cars there that will take you to a restaurant. A great idea these days is to have your Passport with you since you will have to call Canadian Immigration and tell them you are there. Almost every week end something is going on. Music, bands, many vendors for T-Shirts Etc. When you are at the Marina you are downtown Kingston. There is a large field right there for what ever is happening and there are many restaurants that you can easily walk to. Reservations at the marina are a good idea. Don't be surprised to bump into folks like Dan Ackroid who is there a lot, he may live close by. Also don't be surprised to see a 110 foot yacht with some one like Celine Dion on it. The place is a favorite for many.
Also on the American side you don't want to miss going the Alexandria Bay. A great little party town and going to see Boldt Castle on Heart Island or the Singer Castle. Just google them. If you get a chance go to the 1000 Islands in upstate New York don't pass it up!