Not all dogs like to or even be able to swim

My smallest dog, Scrappy loved the water as a puppy. When he was young, he'd sneak into the bathroom when my niece was bathing and jump into the tub with her. He loved the water and would swim and play around. Now that he's older and about twice the size, he has no interest in swimming. We've tried taking him to pools and beaches, but he wants no part of it. I'm not sure what has changed, but we still giggle when we recall the story of the first time he hopped into the tub during G's bath.