You can enter any human-powered boat into the event, no sails or motors allowed, sorry. 
All boats must be "seaworthy" if you wish to do the event in a finer boat please contact the organising committee. 
You can sign up for the entire distance or you can swap at Foyers which is roughly half way, this means at Foyers you must have another crew to finish the course. 
If you need to hire a boat for the event, please contact the organising committee and they will do their best to support your challenge.