If there's no carcass (because I'm not hunting) and every indication that I'm shooting clays (thrower, clays, lack of blood) a CO would be more than bold to attempt a charge of hunting. And once again, where is this quote that states 'no loaded firearms in a boat' because I still haven't found anything that pertains to the discharge of a gun from a boat without regard to hunting. And once again, there is NO HUNTING involved. As far as the US coast guard goes, I really don't give a crap as long as I remain in Canadian waters. I am Canadian. BTW, I assume when you say that it would be bad to not have a licence and targets if CO showed up, you mean hunting licence? Why would I need a hunting licence if I'M NOT HUNTING? Of course I'd have my PAL on me.
Zeus, I just came upon this post (cross-referenced from another). I know this is an old post but I know you want your answer!
The "carcass" part is irrelevant. If I am in my boat with a shotgun, decoys, and a duck call then I'd be hard-pressed to prove i am not hunting when stopped by a CO. Bit of a reverse onus, I'd think. You actually don't even need a weapon/firearm/knife/bow to be "hunting" by definition. If you are harassing, pursuing, chasing blah, blah....you're a hunter. (dogging deer for your hunting friends, paddling after geese, etc) But, I digress.
As for being "anchored".... Hmmm, I shoot ducks and geese without being anchored. As long as the motor is off and I have no forward motion from the motor I'm within the law while shooting migratory fowl....not anchored.
As for the unloaded in a boat thing..... I seem to remember the Firearms Act section 10 saying...An individual may transport a non-restricted firearm (shotgun/rifle) only if it is unloaded. I'd assume they mean 'motorized vehicle/boat". In fact, if you look closely at the regulations to the Fish and Wildlife Conservation Act you'll see that it says "it is illegal to have a loaded firearm in a motorboat. The definition of a motorboat is a boat with a motor attached. The only exception is the geese/duck thing I mentioned above.
The Migratory Birds Act, Firearms Act and Criminal Code are federal laws. The Fish and Game Act is provincial. Both police and MNR-CO's are empowered to enforce all of them. EVERYONE, whether they are hunting or not is subject to these laws at all times.
As for the US Coast Guard.... They can't do a thing, like you said. They're American, and your GPS shows that you're still in Canada!
Hope this rambling answers any of your your Q's. I think the problem with the Internet is that guys just blurt out their version of the law, as told to them by an uncle thirty years ago, or a tale told at a hunt camp after a few beers.... Just a knee-jerk reaction to an awkward question. Always best to research the Act yourself, or ask the authority, as you know.
One of the best conversations I ever had was with a Conservation Officer, while he was checking my hunting licence! We talked for an hour plus. Great guy, and I've called him since.