At least I know how it happens. I must say it doesn't take long. I was only 2 feet away this time, standing in the bathroom waiting for the tub to fill. In one swift move he approached the bathtub and slid in. It was really quite graceful. One fluid movement, out one second, in the next.

Then, splash, splash, splash.
(P.S. Diapers weigh a whole lot after a bath.)