Definitely wasn't a DCC. At the time I'd only been in the country about a month, so I only thought "Oh, they have Snakebirds in Canada as well". Even though I didn't pay all that much attention (at what I though was a common bird), I'm be pretty suprised if it was a mis-identification; I'd see them daily in Perth, Australia (albiet a different species) and they're pretty unmistakable. It was swimming at the time, and I can't think of too many other waterbirds that are that distinctive in the water.
But of course, I'm only human - but if anyone else has any suggestions as to what it could have been, I'm open....