Cecil,
The large burrows and diving in the water to escape remind me of Norway rats. They're omnivores, and like to snack on dead fish, insects, animals, or any garbage'. If they're really big (not muskrat big, but almost a pound sometimes)and have darker fur than standard mice or rats, it's probably rattus norvegicus (sp?).
Thanks bobad. They are nowhere near the size of muskrats and they are gray in color. I'll have to get a pic. They also like to nest under the boat when it's up on dry ground, and in any plastic culvert pipe if it's left on the ground.
