Chiropractors for years have accepted that ball training is awesome. It’s something I certainly recommend for someone who is sedentary, like most of Seattle’s chiropractors, we see a lot of patients who sit at a computer all day long. I know I do working in Downtown Seattle! I usually recommend ball exercses to almost all of my patients, telling them to lay over the ball and let gravity stretch them out. However, sailors are a different breed… they need to do extended sit-ups to hike their weight out from the boat. That’s why I was so suprised to see this picture on Sailing Anarchy.com, with top Laser sailors using the ball for better balance on the boat. 
You can see that this is a really small boat.. It’s pretty ingenious to try and use it for sailing, and gets tme to thinking what other sports it could be incorporated into. Bowling? Tennis? Seems like sailing may be the only one I can think of! Cool, nonetheless.