Aww, that would be so cute ^-^. They could have swimming lessons for Sam and Oscar since the tub is the size of a pond. Dean would have to watch those two closely, they are very smol kiddos.
Oscar would probably only be convinced to try if they gave him something to float on like that rubber duck. Poor little guy would fit down the drain, and since he’s generally so nervous, they’d need to sweeten the deal. And then he might just stay on his ducky the whole time. XD