Actual duck blind question; What are some of the ways people attach plastic 55 gallon barrels to a swim raft/dock or a duck blind? Do you fill them partially with water to serve as ballast?

I've seen guys box them in with 2x4's and ratchet strap them. I've heard of guys using the packaging strap that they use to bundle shit up on pallets with...not sure what exactly they're called though.

We boxed ours in with 2x4 and then used chain to secure it in. We would put a heavy screw through the link into the board.

Like said above, use the 2x4 or 2x6 to box them in, then I drilled small holes in the deck, and used 1/4" stainless cable to hold them in place.
I'll see if I can dig up a few pictures.

We used seat belt webbing, with a grommet in both ends of doubled belt. Bolted through two by six using fender washers. Still being used after 6 seasons of being froze in ice and dragged off island, when beached.