Cheap Medicine or Weighted Balls

I was watching the old Nolan Richardson video "Razor Back Attack" from his days at Arkansas. He was working a three man weave with what he called "water balls" which are simply basketballs filled with water.

What a great, cheap way to get medicine balls or those heavy balls that cost so much! We all have a few worn out or older basketballs lying around that we don't use anymore. Why not fill them with water and make them useful again? I wouldn't dribble those things on the floor, but for passing and medicine ball work they would be great.

I haven't tried it yet (and a google search turned up nothing), but I would assume that all you do is put the needle in the ball and slowly pour the water through the needle - of course deflate the ball first or you'll have a mess! One thought is to fill the bathtub, deflate the ball, and put it in the tub with the needle in and let the water flow in. Any other thoughts? Reply and let me know!