Just plain odd.

[DrNiblik]

Oh! Well the recue dog thing makes sense! And the Nanny too! Like that dog in the old Peter Pan cartoon

[New Found Newfoundland Fan]

That's simply your Newf being a goof. ^.^

I can guarentee that isn't a display of agression. Newfoundlands are amazing nurturers, and are actually still implemented for active water rescues in their homeland of Canada.

Your Newfie is young. All dogs are playful when they are adolescent. When they act in their odd and exceptional ways, they are exploring the social and behavioral boundries that are inevitably established between themselves, and other dogs and people. If your Newf crosses one of those boundries with another dog, they'll be notified with an alarming reaction.

I wouldn't suspect a Newfoundland to deliberate, or indeliberately harm or damage another pet. They're kind, gentle, affectionant, and easily enamourable. I don't think anyone would consider those arguable opinions.