Cleaining the bottom of a boat while it's in the water is a chore few people enjoy. Some people use scuba gear. Some people HIRE people with scuba gear. And there are those, like me, who just jump in a try to hold their breath long enough to get the bottom of the keel. (actually I don't do this any more).
And, of course, it depends on how big your boat is, and how serious you want to get.
Someone told me about this thing, which has been available for quite a while. A little pricey, and I'm not sure how easy it is to lug around. And then if you don't have electric power in the vicinity, your out of luck. But it does seem having a look. You check it out here: http://www.supersnorkel.com/modelSSE.htm