Boat Zoap and bleach. If you have gelcoat
porosity, this can be permanent staining and a big deal. Don't let it sit after a dew fall, clean it immediately. If it gets damp and then sits there it will stain. There are generally rules about this stuff. I'd visibly photo
document it, and then ask nicely for it to be taken care of. If not dealt with responsibly, I'd go to yard management and let them know you will be contacting the EPA to mention the highly illegal bottom paint
dust all over your boat. It will be dealt with right away, but you may not be welcome there again. Sounds like it would be no loss.