Our old Bernese Mountain Dog Buster was truly terrible from about 9 mths to 3.5 years. After that he became much calmer and able to handle excitement. He was my familys first dog, very much loved and will always have a special place in my heart but no one taught him appropriate play with 4 kids under the age of 12. Up at our cottage he would 'herd' us in the water and nip at us or try to swim "with" (read on top of) us. My Dad thought he was trying to protect us and being cute... I usually point out that he wasnt the one getting bitten.