In general this will be at the discretion of the boat owner, although some European countries do require an ICC certificate (equivalent to RYA Day Skipper) for boats over a certain size. An RYA Day Skipper certificate is usually a safe bet for most boats, or submit a sailing CV if you’ve done a lot of boating but never taken this out. Smaller boats will need less experience, but boat owners will usually like to know that you’ve at least handled a boat before. If in doubt ask the boat owner, and there’s always the option of booking a skipper for the trip which has it’s own benefits and will allow you to kick back with your family and friends and relax into the sail whilst someone else gets you from A to B. Hostesses are also available for meal provisioning, and full crews for larger boats. See the optional extras on each individual boat listing for what’s available.