HF Grounds and AC/DC Grounds

My question is about grounds. In particular whether radio grounds should be “isolated” or at least separate from The normal DC ground (negative terminal, engine block, keel or ground plate).

Seems to me if they are separate they may still form a circuit and therefore current through the saltwater outside the boat. So may as well make them all common.

This question related particularly to HF ground installations which are all to do with conductive surface area (capacitance) close to the antenna base.

The question is after the large surface area ground next to the HF tuner should I run a short thick wire to the common ground of the boat?