My car stalls, mechanic lookded at it and said that I had no spark, then he said it could be water in gas tank, or just I need a new transmission, so I still think it is the camshaft sensor??

I think its time for a new mechanic.

I agree with smoothy. If he actually diagnosed no spark, he should have worked on that before speculating about any other possible causes. Take the car to a dealer or qualified professional mechanic and get it properly diagnosed.

Wait... wait...

Your "mechanic" said that you have no spark... then he said it's water... OR it MIGHT be time for a new transmission but you THINK it's time for a cam sensor?

WHAT?

Who is this guy? Find someone else to look at your car.

Do you or don't you have spark? Where did the idea of water come from? Why is it possible that the transmission is causing stalling? And then, why after all these other possibilities do you think it's the cam sensor?

You need to start somewhere... guessing is not the way to solve this.