We were up the Cohansey in 2009/2010. I don't remember any
depth or entrance issues at all. The river is wide and deep for a long way. There is a yacht club several miles up the river and there are boats in it with drafts easily 6', and probably more.
My
advice is that if you get a favorable
wind and
current to simply go all the way through the bay, or at least to Reedy Island anchorage at the mouth of the
canal. That bay is a bummer when things are against you.
Mark