Yes, they do need water - a reasonable sized tub that you can tip out is useful for small numbers of Geese.
My tubs are about 3ft diameter and a foot high and I can turn them over fairly easily.
Commercially I believe they take the access to water away at a certain point and keep them inside on pellets only for the last 6 weeks or so to prevent the meat from becoming too tough (not 100% sure on that though, it's a while since I read about this sort of thing).
An Electric fence is the way to go. A 4 ft pig wire fence with a separate electric wire strand on stand offs - 6 inches off the ground, 2ft and 4ft will normally stop the foxes. The fox can't dig and to jump over has to put his paws against the wire before jumping and will touch the middle or top wire.
The trick then is not to shoot foxes in the local area - they will learn once they touch it not to try to get in again. Foxes are territorial and if you shoot them, new foxes will move in to the area and challenge your fence, maybe getting in this time...
You need to keep the grass short / test the fence to make sure there are no shorts to earth that make it less effective. Since it's such a high voltage, even a small branch or some grass can short it out and make it useless.