Well I've done a bit of sailing but nothing at your level - understand some of it, but not all. In which case, Molly, big it up in your 'hobbies and interests' - it tells people, indirectly, that you're a team player, can follow instructions and think quickly under stress. It shows them that you're physically fit and that you are capable of committing to things long-term.
You *could* make out two separate CVs and then use the same general cover letter. The letter only needs to be brief, as you'll have most of the important information in your CV. Just something along the lines of "I'd like to be considered ... As you will see from my accompanying CV I am experienced in XYZ ... I would like to work for you/your company because ... etc." As long as your letter is properly written and set out, that's all you really need. Think of it as an introduction - when you meet someone for the first time, you usually just shake hands and announce who you are and, probably, what you do or where you're from. You wouldn't give them your entire life history. They can delve further (ie your CV) for that.
Good luck, though. Let us know how you get on.