I've been told that the front-crawl was a Native American way of swimming, which Europeans adopted. Apparently, the Europeans of this time used the breast-stroke, but this would've been c. the late 1500s I guess.
But what about 500 years before that? I would think Vikings or just sailors in general knew to swim, but how would they do so?
This is tangential, but it is clear from a copy of Bellisfortis included in Hans Talhoffer's 1459 manuscript on combat arts that human bouyancy was a subject of study; http://commons.m.wikimedia.org/wiki/File:Ms.Thott.290.2%C2%BA_014v.jpg Notably, an inner tube of stitched leather filled with air.
Barbara Hanawalt's book The Ties that Bound uses a lot of legal documents, especially coroners rolls, to describe peasant life in Medieval England. According to this book, deaths from drowning were relatively common and she infers that most peasants were not able to swim. There are records of some dying in roadside ditches and fishing ponds, which seems to confirm her view.
