All dogs that are treated well will be good protectors.You want big dogs means like Labs, German Shepherds, Doberman Pinschers, etc. or any mixed breed dogs will do as well.
I loved Mammoth Lakes! My B/W Nika was like that. Always looking for the spot to jump over the water. Did not like walking on wet grass. She'd tolerate a bath now and then as long as the water was nice and warm.