Sperm cannot survive the pH levels of the water, nor the temperature. So as long as there is no direct genital contact, there is no risk.
Direct, unprotected genital contact always presents a pregnancy risk. So yes, your shower scenario could present a risk. And I would hope your partner would be cleaning his foreskin daily, because i'm sure you could develop bacterial infections from old smegma trapped under the foreskin.
Copyright 1998, 2013 Heather Corinna/Scarleteen
Scarleteen.com: Providing comprehensive sex education online to teens and young adults worldwide since 1998
Information on this site is provided for educational purposes. It is not meant to and cannot substitute for advice or care provided by an in-person medical professional. The information contained herein is not meant to be used to diagnose or treat a health problem or disease, or for prescribing any medication. You should always consult your own healthcare provider if you have a health problem or medical condition.