Swimming Lessons

Can a person have a gene for buoyancy, inherited from his mother and grandfather?  Finn is a fish, as comfortable in the water as if he were born there.  No fear--jumping, diving, staying under water.  Pool, ocean, lake, or bathtub.  So, swimming lessons were successful.  While waiting om the wall for his next turn with the teacher, he preferred to hang out under water, but the life guards were happier when he stayed above.