BC game laws are kind of vague, in that if it isn't specifically listed in the wildlife act as being illegal, it is legal. That's why spear hunting, slingshots, air guns are now specifically listed as being an illegal method of take for big game. Until recently they were legal by default.
Using shot for waterfowl that isn't non toxic, is specifically listed as being illegal. If you wanted to hide under the water and grab geese by the feet as they swam over (and I would pay to see that...) it would be a legal way to take geese. You likely won't ever see it being illegal to dispatch a duck or goose with your hands simply because a lot of cripples get killed that way after being returned to hand. Should it become illegal to do so, then there would be a definite rise in the number of close calls when a dog returns a lively mallard to the boat and you have to shoot him because you can't ring his neck....... Although, it would probably make the excuse of "boating accident" way more believable when the Federales come to the door to take your shotgun if a bunch of boats have had holes shot in the bottom of them....
Water sluicing, legal. But as said, frowned upon by some.