>How about the largish water mammal being a river otter? They are
>good-sized, pretty tame & curious, too?

That's a good possibility, as otter have stoutish tails, play around
in the water (my nutria suggestion is a bit of a reach since I've
usually seen them swimming somewhere rather than simply swimming), are
about the right size, and quite common. A good look at the face
makes it clear they aren't rodentish critters, though, so in this
respect at least they don't resemble beaver.

- Don Baccus, Portland OR <donb at rational.com>
Nature photos, on-line guides, at http:://www.xxxpdx.com/~dhogaza