How can you melt chocolate without it getting wet?
The way you've described is precisely how I melt chocolate.  If you have a double boiler, that's even better, but a bowl on top of a pot is fine too.

I can only think of two things that might be affecting the quality of your end result:


Is the bowl big enough?  The melting bowl should be larger than the pot if possible; you want the steam to be forced under and around it.
Is the water temperature reasonable?  You want it to be at a simmer.  If it's rapidly boiling, the heat is too high.


As long as you keep those two things in mind, your chocolate should melt fine!

Edit: Thought of one other thing:


It's possible that the steam is actually rising above the bowl, then hitting something (like your range), condensing and then falling back into the bowl as water.  You shouldn't even be getting much steam with this method, but just in case, turn your fan on, to make sure you aren't getting any condensation.