You can find Water Pokemon at these places: Sinister Woods Silent Chasm Frosty Forest
You get them in dungeons
many
yes some dungeons you can't enter but if you rescue scizor from froslass (crevice cave) you can get to all mystery dungeons
if you buy friend areas you can do it
follow the story of the game..veronica
Yes you can you can find stones in dungeons or get them from rescue missions.
Get the job from the notice board, go down into the dungeons and keep going until you find the pokemon.
You have to go to their dungeons and battle them until the join you.
You have to keep doing rescue missions until rescue missions that have extra dungeons as rewards come up. You can also get the Wonder Mail codes online or elswhere.
It is called that because you explore dungeons and help other pokemon. On the DS, it is blue rescue team, whereas on the GBA, it is red RT,
If you are talking about when you get defeated in a dungeon, in special dungeons the system will ask if you want to send out a rescue statement. (i.e., being defeated in dungeons where you are on a special mission like defeating Groudon or Dusknoir.)
you can't trade on Pokemon mystery dungeon OK