I was sitting on the bank of a little pond hoping the frogs would pop their heads back out of the water and this guy comes swimming right toward me! It stopped a few feet from me and finally turned and went the other way.
Looks like he was trying to scare you away from "his" pond - might have worked for me - but I'd like to think I'd be big and brave like you and go for the shot!
Yikes- no way I would have even stuck around to take a shot of that guy- I'm not sure what it is, but I don't think it's innocuous like a Garter Snake- and I run from them too.