There is another method,if you prefer labour vs material cost & have easy access to football size rock or bricks.
It is the rock filled cribwork.
In ur case,for a dinghy dock
,in very shallow water
,you would build a 4ft sq crib out of 6 " logs(cheap) or 6"treated square stock,as used for retaining walls,gardens,etc. Assemble the square like a log cabin
,only with gaps.(see pic of large wharf),with a plank deck
,sitting on the bottom layer of logs
Float/drag this crib offshore
.Add a foot or two of rock/brick.Build a plank deck/walk to span from shore to crib.
You can add additional support under a long walk with posts with cross shoe sitting on hard bottom,if reqd.
You can add "vertical fender
boards" from edge of walk & driven in bottom a bit,etc,if reqd.
Our old family fishing
wharf was built from spruce & rock in 1920,s & still stands today.