While looking up something else, I came across these ads for dive cruises that actually mention wheelchair access on the boats:

http://www.smallshipcruises.com/siamdive.html
http://www.jst.org.uk/gallery.cfm
http://www.cadvision.com/dsaa/downlo...l_Brochure.pdf
http://www.1cruise.com/firsteuropean/before.htm
http://www.dsahq.org.uk/Verity%20K.htm
http://www.celebritycruises.com/prep...A17A4F5&sid=92
http://www.carleton.ca/cdac/CDAC's_Able_Sale_Page.html

Here is a story from last year about a quadriplegic sailor who is planning to go around the world in his yacht
http://news.bbc.co.uk/1/hi/uk/1454270.stm

Although he had to abandon the trip because of health problems, here is a story about the boat that he was planning to use, and his plans.
http://www.globalinventure.com/