A Neapolitan mastiff I lived with was swimming next to me, he wasn’t super comfortable in water and as we were swimming he bit into my forearm and hit bone.

He didn’t mean it at all. I don’t even think he knew it happened. He was pretty dumb, but that is beside the point.

OP’s advice isn’t actually awful. If I actually had to fight Ben Dog, I would have no option but to go into the mouth. Same for grizzlies. But.... I would not want to do this and am certain I would take a lot of damage.

This would be a case where the only way to win would be to avoid.