Balance: Simple mirrored map well balanced indeed.
Fun: I'ts a nice idea to "allow" players to confront themselves in the water, although it might get dificult cause you start losing health.
Gameplay: As a simple map, there's no FPS problems, you can play at maximum capacity i'd say.
But i'd say the map is quite small and narrow.
Teamplay: Since this is a ka_ map i think it's always very important to have a good teamplay, althoigh as i said the map is a bit narrow witch keeps it more dificult.. you should have made it wider.