Wife`s reaction wasn`t good

A few years ago, my wife was planning a girls night out. She and several friends were having dinner and a movie. I knew the house would be quiet for about 5 hours. After she left, I did about an hour of yardwork then went inside to get cleaned up. I NEVER take a bath, but for some reason thought I would that night. I filled the tub and turned on the jets (its a fancy garden tub with jacuzzi jets). The water on my tired muscles felt so good. The water moving against my cock felt so good. Soon, I began to stroke my erect cock.I guess with all the noise from the jacuzzi jets I never heard my wife enter the house, come into the bedroom, then open the bathroom doors to get a sweater before the movie. In fact, I had my back to the door so I didn't see her either. "What's going on in here?" she asked. "Uh, didn't expect you home so soon" I answered. "We'll talk about this later when I get home" she said.I guess she didn't realize that I (and 99.9% of all guys) masturbate from time to time. She now knows and made it very clear she doesn't like it and insists if I must do it to only do it when she's not around.