before you just rent a boat... think hard about taking a boating course. In addition, I would highly recommend you go out with an experienced boater first.
I was 17 when I bought a little 15' Runabout. I had been around boats all my life, grandfather, uncles, friends, etc. So I wouldn't say it was the first time on a boat. Well, long story short...we could have been killed or worse, killed someone else. Set out for the first time as "captain" with 2 friends, we got lost, arrested, and fined. The next week I took a basic boating course with the local Power Squadron.
USPS Educational Department - Public Boating Education Programs