In Ontario navigability is determined by the following criteria: (1) A stream is navigable in law if it is navigable in fact; (2) if it is capable in its natural state of being traversed at least by small craft, or even, in the Canadian context, if it is floatable in the sense that it is used to float logs, log rafts and booms; (3) so long as it is realistically capable of being so used; (4) the stream may be navigable over part of its course and not navigable over other parts and hence its navigability may be determined independently at different locations; (5) the test identifies a lake or stream as a public water over which the public have an inherent right to pass, whether for commercial or non-commercial purposes. Moreover, the test remains open to definition in light of modern needs of the public; (6) the essence of the test of navigability in law is that a stream be a public aqueous highway used or capable of use by the public.
Source
http://www.interlog.com/~erhard/navib.htm