I was hesitant to share my technique to water padding, because it kind of ruins the mystique of it, but so many of you have asked.  Here is the technique I used (it’s still being refined, though):

Parts:
1. normal, tight-fitting shirt
2. fitted athletic shirt (the kind that stretch to crazy sizes but are still skin tight)
3. a stretchy undershirt
4. a big, dark shirt to cover it all up
5. three trash bags with handles
6. tight pants/shorts or belt

Put on the tight-fitting shirt (1). This is just to keep the bags off of your body. Next, you have to put on the fitted athletic shirt (2) as though it were a pair of pants—legs through the sleeves.

Put the bags (5) within each other as best you can. Loop the handles together, and put one half of them around your neck like an apron. You should be able to hold up one side with your hand and the other side being held up by your neck.

Pull the athletic shirt up over the bags as high as you can. Put a shirt on top of all that (3). Put on your pants just below the bottom of the bags and cinch them up tight if you have to (6).

Fill the bags up with water. I have a detached shower head that I used, but you could also use the sprayer on your sink. Any hose-like attachment. Anything else would probably be too difficult.

It feels strange the first time. Don’t worry about the bags breaking unless they’re cheap or you’re pouring water too fast. You may have to hold up the bag as it fills if it gets too heavy.

Once you’ve filled it up as much as you want, loop the remaining handles over your neck. Put on the last shirt (4) to cover it all up. A darker shirt will cover up the stuff underneath even when stretched out.

The weight can be tough on your neck, and could be too much for the bags unless they’re heavy duty. Don’t try to walk around without holding it up with your arms if it’s really heavy.  If you’re wearing a strong enough shirt/pants, you can also try to tie off the bag and let it be supported by just your clothing, but be careful when trying.

As for the padding for the rest of it, that’s tougher. I padded the ‘chest’ using just a rolled up towel. You might have to figure out what will look best for you, though.

Have fun!  Hopefully I’ll have a more refined technique eventually.