Maybe he just didn't have the right
gear. I've always questioned the "willingness" of that cat. Every clip I've seen of her underwater, she's limp and motionless. And there's footage of her swimming in the pool calmly, but none of her entering the water of her own volition.
The dog, on the other hand, is actively paddling while under water. I can accept that he's not unhappy about it.
The cat? I'm not so sure.