Whitewater kayaking. I used to be damn good, had a spate of shoulder dislocations which basically prevented me from doing any for around 5 years. I am rediscovering it as a sport.
I dislocated my shoulder learning to kayak a long time ago, and it popped out about once a year until I got surgery. I spend a good deal of time in the wilderness, and I am hoping I never have to deal with a remote dislocation that won't go back in.
Also any idea if ACA courses are any good?
http://www.paddling.net/guidelines/showArticle.html?148
No idea about ACA as I am in Europe. In my experience, getting out with other good paddlers is better than any courses, but then I did learn the basics quite a while back. Most instructors in the UK seem to want a (teaching) qualification to prove they were good. Most good paddlers didn't need a qualification.