[DonRotolo]

We've never run one, but the ones I have seen used rubber ducks, not live ones. These can be had at toy stores, or try Oriental Trading Co.

As for private property, it would be the right thing to speak with the owners and ask permission to enter their property to retrieve any 'lost' duckies, so as to not pollute the river.

I can't speak for Connecticut, but in NJ a river cannot be privately owned, the state has an easement to all waterways, up to flood stage.