well, you have a lot of problems cuz the water lines aren't what you think they are, so it will be better if you dont edit water.dat as a text (use 3dsmax for such think to add water in any map coords(this is more serious issue)).
the reason why your cars aren't recognized by the game is because you didnt replaced them correctly.
if a car mod is comet.wft and comet.wtd (for example) you cant replace a truck of a bigger car than the comet (dont rename it, only if the car is as big as the comet car).
if you do, you need to copy the handling lines of the comet in the car you replace line in handling.dat to change the way you drive that vehicle.
if you dont have car mod fails because of this just tell it.