Showering with a friend is a really good idea. You save a lot of water, have someone to wash your back and have someone to talk to instead of singing. If singing, you can do a duet! The idea of “Getting to know you” really applies and one can assume you will either really like each other, or hate each other afterwards. You may just want to make sure that the friend knows you are joining them otherwise things could turn out bad.
How to celebrate – Take a shower with a friend. Save water. Use two different bars of soap.