I don't think I'd have the guts to take my phone into the shower as it was too dear! I suppose the odd splash wouldn't hurt. That's an interesting article on the subject.
Edit: Reading the article, the S4 Active is waterproof to 1 metre.
I've had my S4 for over a month now and I've never had any problems with it until this morning. I tried sending something (from home) and I noticed it wasn't connected to the WiFi, so I automatically assumed it was the WiFi router; which I reset. I then tried connecting and the S4 said...