That is a fun section of river. Must be a blast in a kayak.
As kids we ran it in a canoe. When loaded with gear we'd almost never make it through without swamping. Then we'd unload, tow our boats back up and do it empty.
I remember Mongaup had a lot of water but wasn't that scary, to a little kid.
ETA: I now realize you were probably up that trib. We called that big rapids in the Delaware the Mongaup rapids.