Hi Tim,
Have been asked about cleaning boats in the past, contacted my insurance company and they said I'm not covered! Before even considering the job enquire wether your insurance covers you first.
Aparently planes, trains and boats require extensive cover. Not so much with pleasure cruisers which I have cleaned but commercial jobbies. Can understand because if you fuse out a plane or boat and it can't travel there could be a large compensation claim on your hands.
Charge would be upto you, whatever time and expenses are incurred.
Worth looking into if the jobs a large one........
All the best,
Jason.