Here's a link to an interesting Boat Detailing Article that was in Professional Carwash & Detailing Magazine. Very good information.
Summary of article:
A natural extension of auto detailing, boat detailing offers few barriers to entry. For detailers living near waterways, boat detailing can be a natural extension of auto detailing, with few barriers to entry. Getting started can be relatively easy, but there are a number of considerations before taking on those first customers.