Because they don't need to walk in water. They'd float anyway. I guess.
Do you believe that anyone who is fine with someone doing something wrong might as well be doing it?
Nah, not really. Around 75% of DC is:
-Someone dies
-Someone screams
-Three suspects
-Someone says something that gives Conan an idea
-Conan puts Kogoro to sleep and solves case.
Plus it's fake and not real.