I have built a floating dock from treated 1/2" 4 x 8 plywood, skirted with
treated 2x4s and supported by 9 cable restrained 15 gallon plastic barrels.
Currently I have two of these tied together with 8' 2 x 4s using lag bolts.
The resulting dock is 8' x 8'. I want to double the size with two more
sections for a total size of 8' x 16'.

The river floods occasionally so I will want to be able to take the docks
out. This will involve dragging them up about 12' of bank. I want to
disassemble the four sections to do this. I am looking for a way to connect
the four so that they can be easily disassembled and reassembled without me
getting too wet in the winter. So far, I have bought hanger bolts and wing
nuts that I intend to use with 16' 2x6 boards on either side. This will
work, but it will be very tricky to get all the holes aligned at once.

Any suggestions?