Rub A Dub Dub, Poop In The Tub

Seriously. I can handle almost everything that comes with being a mother, spitting up, full on projectile vomiting or pooping, and really yucky diapers. What I can't seem to handle is the pooping in the tub. Really? Why the tub? It happened not once, but twice tonight. I filled the tub up and she poops. I empty, clean and refill the tub and she poops again. So, I yet again, empty, clean, and refill the tub. She has done this several times and every time I see her starting to go I immediately put her on her potty to go or to finish, but no such luck, she keeps on pooping in the tub.

To all you mothers out there! How do I stop this from happening again? Please any advice is helpful. Thanks!