Public Domain Review has scans from "Illustrations from Everard Digby’s De Arte Natandi (The Art of Swimming) published in 1587, considered the first English treatise on the practice." Here's the complete set.

http://feeds.boingboing.net/~r/boingboing/iBag/~3/eShNo4LNXGM/how-to-swim-an-instructional.html