So many comments running through my feeble mind.
A. take it to the yard, have it hauled. Gotta be less expensive than hiring a diver to clean the hull
B. be careful now much you chip and scrape off that hull. That marine growth may be the only thing from keeping the hull leaking.
C. That is not my boat.
D. if a boat I was interested in had marine growth like that, I would strike it from my list of 'boats to consider.' If the bottom is that bad, the rest of the boat must really suck.
E. I wonder if the owner is still alive.