Glad your dogs OK, the same thing happen to me years ago down at willapa, the weather had been below freezing for about 7 days and I shot this mallard and it landed in this small fresh water lake just inside of the salt my dog had to brake some ice and he was on his way to getting the duck when all of a sudden 5 otter came from no where and got to my duck first 2 otters grab the duck and the other 3 came at my dog doing that hissing, I shot up in the air and the 3 otters that were coming at my dog took off with the other otters with my duck. I was abel to get my dog back safe. So now I am always looking around for otters. Be careful.