hmmm personally gravity bongs are really easy to make.

take a small bucket and a bottle (a 20 oz. or liter bottle works good) and cut off the bottom of the bottle. take the lid and melt/cut a whole in the lid and fit a small ratchet thingy in there for the bowl.

Then, Pack a bowl of 'tobacco' and fill the bucket with water. Next, submerge the bottle most of the way (don't get too close to the bowl.) Light the bowl and slowly pull the bottle out of the water to fill the chamber with smoke. once it is almost all the way out of the water unscrew the cap and hit that thing like a champ lol.

i'm really sick and not thinking straight so i hope that made some sense.