My corgi Chloe dove into the pool exactly like that, but didn't use a life jacket. We called her "Underdog" after the old cartoon dog of that name who looked just like that when he flew . It was entirely self-taught. We introduced her to water in the pool gradually, as she was initially frightened. We sat on the first step with her in my lap for a couple of days, went down to the second step and so on. But, she was afraid of water so deep that she couldn't touch bottom. So we put her on a big float and she figured out how to maneuver it by running back and forth on it. One day she just jumped in the water and thereafter swam every evening with my husband, especially enjoying jumping in after tennis balls. She was so cute.