[Pblais]

Gord, I think you have it and it and pretty much rules rules of thumb. Military ships sort of fall into a similar category based on the basics so it works for them pretty well. Recreational boats being lighter mass have more variations.

A beach ball floating on the water vs a 10 knot breeze and 6 knot current can have almost any current you can imagine and be blown where the wind goes. In the extreme example comes the answer. It all depends on how much of the above and below the water is exposed vs the mass of the boat. Submarines are not effected by the wind.

Newtonian physics says Force = Mass X Acceleration In this case we subtract the drag for each effective fluid as noted.