Probably very small snake chaps are your best bet. Buy half as many as you have fish and use only one leg from each per fish. Seriously, though, I don't imagine there is any way to entice moccasins out into the open. In Alabama, at least, if you do see a snake swimming and the snake gives the appearance of being mostly on top of the water instead of at or just under the surface (and especially if the head is out of water while actively swimming), it is almost certainly a moccasin. Water snakes are thinner per unit of length and swim through the water with their heads on the same plane as their bodies. It is important not to count on black vs. brown as an identifying feature. The color of moccasins varies from one to the next and also with age.

In the spring, I used to keep a little 410 in my boat and popped ‘em as I saw ‘em. After April or very early May, they rarely came out into the open. As I mentioned in another thread, now that we have so many geese around, we hardly ever see a snake either in the water or around the house (which is on the shore). We still have to watch where we put our feet, but that is because of the goose's number one product.
Lou