You can absolutely teach your Newf to jump into water. This is a necessary exercise for Water Rescue (WRD). They need to jump off a boat deck two separate times during that test. Believe it or not, there is a technique to teaching them to jump. You want a jump that is long, and level to the water, as opposed to a "kerplunk" messy jump. There are a bazillion different ways to teach this. However, with Hemis joint issues, I'd avoid teaching him this technique on land first, which is where many of us start. First though, I'd make sure he was SUPER comfortable at swimming, before having him jump. Meaning, he is totally level in the water, and takes off swimming without hesitation. Because once they jump, they have no choice BUT to start immediately swimming and one scare from a bad jump will set you way back to square one. I recommend doing it with a doggy lifejacket when you attempt it until he really gets good at it. This will prevent him from his head dunking underwater after the jump, getting water in his ears and getting spooked. Boj is a fantastic, very strong, level swimmer. In fact his topline stays dry he is so level in the water, HOWEVER while training him to jump he always wears a lifejacket until I know he has it down perfectly. This is our major exercise we'll be working on to prepare for the water test this July. You want them to stay focused on something WAY out from their jump point. Whether it's you calling for him, a toy, etc this will promote the most ideal jump.