I own a fantastic 15 week old pup that can flat arse mark...on land!!!
Her breeder introduced her to water at 4 1/2 weeks. Swam like a fish!!! At 9 weeks old I started to slowly reintroduce her to the water. Instant puppy paddling. Several times I’ve tried to get her back to leveling out and swim properly. She’d level out once she had a bumper in her mouth. Other than that. Head straight up, butt down, and puppy paddle.
Today my wife suggested putting her in a small doggie life jacket to see if she’d use her back legs and level out.
I took her into the pool and slightly lifted on the back of the jacket and she swam nicely to my wife several times.
When she swims towards me she puppy paddles.