I hunt on the Mississippi River, and hunt out of a blind in the middle of the river. Can i still use a flag for geese? If so what lenght of pole and what kind of flag?

I would think that flagging would be effective...you could make your own with a piece of conduit and black material for low cost....

it should still be effective as long as you dont over use it and it doesnt have to be that detailed if you make your own