Not sure if you mean personally taking a boat and crewing it your self, or joining in an organised tour/sail? There are many companies that operate trips around the Whits with all different prices and itineraries to suit any pocket.
A couple of websites to have a look at are http://www.sailing-whitsundays.com/ or http://www.whitsunday-yacht.com.au/ with the latter one giving you options to crew your own boat.
Departure point is usual Airlie Beach and there are a lot of agents in Airlie offering trips. about 8 years ago