Teh move fly is important, but water attacks are more important. Especially if it can learn ice-beam.

Depends..on the game and what you're doing because in some games you get surf before fly-a good example is Emerald and Houen games and both could be useful especially in Soul Silver/Silver/Crystal with Whirlpool or even with the Houen games with Dive and that's how you get to the eight gym and you can't fly there unless you've been there..so it depends really as I've said.

I think water type is important because some HMs (Whirlpool, Surf,Dive and Waterfall) are water type moves

Water type can take down more types than Flying, like Fire, Ground, and Rock. Flying can only take down Grass and Bug.

Both. I usually carry one Flying type, one Water type, one Fire type, and one Electric type. If I have one, I'll carry a Dark, Psychic, or Ghost type. I leave the last spot for any other type I might need.

Water expesialy in battle. and you need to know surf,Waterfall,dive,and whirlpool. Though i do agree fly is nessiary to have water is of more importance

You need water types hms like surf waterfall dive and whirlpool to get around, fly is like a teleporter, not needed but useful

But if you have a Swanna you won't have to make this decision! xD

In my opinion.