Judging from your two posts, I suspect your English is more than sufficient for an overseas TESL position. Look into it and you won't need to worry about a job. (oops, I'm already assuming you're in N. America and not already overseas!)
As for living on a boat without experience; Living on a boat, at dock, for a summer is no different than living in a small, inconvenient apartment with fewer facilities and less amenities. If you actually want to sail the boat, then yes, you'll need training; There are many opinions and options for training, from formal training to hands-on/real-world experience. In the end, you'll need to learn the laws as well as seamanship in order to keep your home/boat safe. Think of it this way, you, an 18-year old, pull into a new harbour... you have two options; one, you come in too fast or misjudge your docking, colliding with expensive boats and make a fool of yourself showing that you are a knotty-headed junior. OR, you arrive in port in a seaman like fashion, kiss the dock and step ashore to earn the respect and admiration of your fellow sailors. Which do you think is more likely to occur if you don't have training?
It all depends on who you are, what your experience and situation is. For me, I look at some of these tall ship programs and wish I had known about them when I was younger (as well as had the money to try them out). I like that you already want to break-out from the 'norm' and routine of what your friends are into. That's a great start.