The Bears two cents:
My wife can tell you about this. In ' 72 while sailing off the west coast of fla. we hit a" Niger head" no inferent intented, large brain coral growth, with our keel running at about seven knots. She was thrown into a bulkhead and suffered a slight brain concussion. We sailed on into Tarpon Springs where she went to see a doctor who concluded she did indeed have a slight concussion. Under water inspection showed that there was damage and the repairs required hauling the boat and some major reworking the front face of the keel and hull. My company insurance was understanding enough to cover the expense of the doctor. My boat was not insured. Let us say "feaces occur".
Charts do not cover ever square inch of the sea and thank the builders of a certain line of boats for over bulding their craft. It could have been much much worse. There was no major hull integerty breached and no craft ability restricted but that was shear blind luck.
When you hit a large basicly imobile object with a large (several tons) object moving at even a low speed major problems can and will arise. First, check the crew and passangers, attend the injuries as best you can and put somebody in charge of their care. Remember you as captain are in overall charge and you have many other things to take care of; so "Deligate" . Check the condition of your craft. You are in a hostile envierament, the sea. Secure you craft! Call for assistance as necessary. Check back on the injured. Advise "help" of the conditions on board and of your craft. Insure the safety of your crew and passengers.