Sounds like magic to me, but, 4Moms claims its Infant Tub lets the clean water flow in whole making the dirty water go out.
And with the built in color-coded temperature gauge, “it’s easy to get your baby’s bath water to a safe and comfortable temperature,” the company says.
Okay, maybe not magic: it requires three AAA batteries. But it fits single and double sinks. It’s $50 here.