On the eve of Al Gore's Live Earth gigs in July 2007, Jennifer Aniston said that because every two minutes of showering uses as much water as an African person has for an entire day, she restricts herself to a three minute shower (why fuck just one African's day up?). Also, she pointed out that she brushes her teeth in the shower to save on water, and that she painted her house green so it could be powered by photosynthesis.
OK, we made the last one up.
So What's the Problem?
For the moment we'll forgive the fact that dentists say it takes two minutes to brush your teeth properly, leaving Jennifer only one minute in the shower to clean the rest of her body (though perhaps making it clearer why Brad Pitt left her).
The bigger problem is that two minutes of brushing in the shower uses about five gallons of water, where two minutes of modest faucet usage (even if you're the type who leaves it running the whole time) only uses about two gallons. You don't need a spreadsheet to tell you which one saves the most water. Also, we can say from personal experience that you can save way more water than either method by simply not showering at all.
It Could Have Been Worse...
She could have suggested just taking your toothpaste and brush to the car wash, then sticking your head out of the window as you go through.