Ignoring special circumstances like St. Pierre et Miquelon, it’s customary, when the “territorial sea” claims of two countries would conflict, for them to draw a line roughly equidistant from both countries’ shorelines and define it as the boundary between their territorial seas. Much of the Pacific is divided up in this way, and the North Sea is a very special case, in which the claims of something like seven different countries conflicted, and were carefully negotiated out to give everybody a share of the oil field. Presumably there is already a line between the Bahamas and T&C, which would remain in place. (And no, you can’t have a strip of ocean connecting Sable Island with Grand Turk! :p)
Spoilsport 
I spent some time in the Turks and Caicos. So here is what I know. Briefly inhabited by British loyalist after the American Revolution. Only took about 10 years for them figure out that salt raking pretty much sucked. They departed leaving behind thier slaves. Remains a British Crown Colony. There is no way to become a citizen of T&C. You are a “belonger” or not. You can get a work permit or resident status if you are sponsored or make a generous contribution to the islands. Of the non citizen residents, most I met were either French or Canadien. One possibility someone elser mentioned is true: Slight refugee problem from Haiti. The only industry is conch farming. Tourism provides most of the revenue and there is offshore banking. It is a hot, dry place. No fresh water source. All homes have a cistern and rain water collection system. There is water delivery available from desalinization but it is expensive, like everything else on the Islands. Electricity is VERY expensive. Air conditioning is a real luxury and few have it. A jar of mayonaise cost me $7. Provodenciales, where the airport is, is a strip of sand twelve miles long and a couple miles wide at the widest point. There is one poorly paved highway that runs the length of the Island. They drive on the left with automobiles designed for right hand driving. Pine Key is uninhabited for the most part, with just a few very exclusive resorts. Beautiful place for a getaway. Grand Turk is the center of government and the place for most provisions to be secured. Salt Key is a speck of an island to the east but also has resorts and dive services. Those are the Islands I visited. I think North and South Caicios are also inhabited but sparsely and mostly by natives. The place is reputed to be one of the top diving destinations in the world. There is no frsh water on the islands so there is no sediment deposited into the surrounding water. It is by far the best quality of diving I have seen.
So anyway, Should Canada annnex T&C ? The sense of pride and independence I got from the locals would make me wonder if that is something they would want. And it is basically a few rocks and some sand in the blazing sun so is it something Canada would really want ? It is a tourist destination but I suppose many, like myself, feel like they have seen it all in one trip. Unless you are a complete diving freak, there isn’t much else to do. One small casino on Provo and then there is “The Hole”. A limestone hole in the ground that is listed as one of the top things to do on Provo. C’mon, it’s a hole in the ground. And not a very big hole.
according to the CIA World factbook entry, they already claim 200 nm.
http://www.cia.gov/cia/publications/factbook/geos/tk.html
I think this is an extraordinarily cool idea.
You’ve obviously never been to Windsor, Ontario… Grew up there - not much to do… Other than go to the one Casino… and after spending the first 20 years of my life there, I still call it A Hole after moving away 17 years ago…
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Oh…
THE Hole…
Never mind… Carry on…
Survivor
But still a member of the Commonwealth. Aren’t the members supposed to take care of each other, be allies when one is invaded? Otherwise, what’s the point of even HAVING a Commonwealth?
It makes the Brits feel better about not having an empire. 
Originally it was to build up a UK lead organization, kind of like the Organization of American States. It’s about as useful. Well to be honest it did help with apartheid in South Africa (led by Canada), but has completely fallen down with respect to Zimbabwe (abetted by Canada). It suffers the same problem that most multilateral institutions have when it comes to human rights; many of the members that are needed to make a common front are equally guilty of the same crime.
There is no real treaty involved (economic or military).
Right. The commonwealth is not an alliance, like NATO; it’s more of a group or club, like the Francophonie or G-7.