I was using the frame of the dock for locating the posts initially I tried the red 0 degree nozzle but lost it after the quick connect unlocked while moving it up/down under a post. Turned out the yellow 15 degree nozzle worked better. I set the post upright used a piece of string to tie it off to the frame plumbed. Just worked the jet around the post in the perpendicular plane then slowly undermine the bottom material. I made use of a fire brick block that was laying in some old materials dumped for seawall erosion. Set it on top because the posts wanted to float after going down a couple feet. I grabbed a bunch of bags of pea stone from the local Ace and poured them around the posts and over time the mud and sediment should lock them in.
I know this thread is a bit old, but I came across it and wanted to ask how the 5x40 finger dock turned out after the setback hassle Did you ever get the bracing figured out for the posts once they were sunk with the water jet? I’m planning something similar and curious if square posts held up better than round ones would have
