I'm sure you all will think I'm nuttier than I am. But, I built my 12'x 12'dock platform with pressure treated 2x12 bands and joists. I decked the platform with pressure treated 2x6s. I pushed it into the water with my tractor, hoping it would float. It did.
A friend then helped me put the barrels under it, starting at the four corners. A few days before needed the the barrels, we sealed the threads of the openings (bungs?) with RTV, and then screwed in the caps. After the water warmed, and w could be in the pond, my friend and I dropped the barrels into the pond one at a time. We were able to push them down far enough into the water to get them between the joists. The more barrels we got under it, the easier it got. I'm not sure, but I think I've got 12 barrels under mine. Nothing holds them in place except their flotation.
My barrels do collapse a little in cold weather, since they are air tight.
This is my third season with this dock. We get at least 10 inches of ice every winter, and it hasn't affected the dock in any way. So far, so good.
