From what I found on the Internet, a brief shower is more water efficient than a bath. I was wondering if there is any research about water use with more than one person using a shower? My gut feeling is that two people showering uses around 150% of a one person shower.
Notoriety is established with the the following catch phrase Have a shower with your fella, Stella which was part of Australian government TV campaign during water restrictions a few years back. (Cited here and here.) The implication is that two-person showering saves water.