Sorry about this basic question, but how do you start a flight away from an airport?

I assume you wish to start airborne rather than on the ground.If so, start up a normal flight and get airborne - when you reach the desired location, just Save that flight (the semi colon is the shortcut) and give it any name you wish.When you start FS2004 the next time, go to Select a Flight and choose the one you saved. You will start at the point you saved it.Hope this is what you had in mind.

Yeh that's great, but if I wanted to start on the water would I do the same thing?

Yes - you can save a flight at any point and that is where you will be placed when you select it again.The saving process saves the aircraft you are using as well as the location and weather etc.

Thanks.

If your plane doesn't have wheels, can you swap planes?

If you are interested is "water airports" I would also suggest that you downloaded uswaterrunways.zip from Avsim.It is a comprehensive listing of all the seaports or water runways available in FS2004 and was compiled by Mike Davis.Knowing where to start is half the battle!

thanks again.