Need a water balloon but got no balloon? Regular old paper and skills of a fold-ist will have you drenching your foes in no time, with stile to boot.
Step 1: Parts Layout
(1) a sheet of paper
(2) a second resource for showing how to do this origami: http://www.fishgoth.com/origami/basics5.html
Step 2: Square Your Rectangle
tear (or cut) paper to make it a square. Fold the paper as shown in the picture and tear the flap. A clean tear can be made but folding along the tear line multiple times and licking along the crease (avoid paper cuts!) then tearing.
hopefully the pictures on this slide show what's going on.
Step 3: Fold and Label Square
Make creases from corner to corner and mid-point to mid-point across the square. A good crease forms when folding the same line forwards and backwards a few times.
Then, label the ends of each line as shown in the picture. (these labels can be "mental labels," for book keeping)
Step 4: Begin to Fold...
...but don't give up! (get it?)
fold points 1 and 2 onto 3 and A to A' and B to B'. Do it in one fluid motion and it will look like the picture.
Step 5: Fold Up Corners of Base
now that you have this folded-alot-triangle (from last step), fold the two free edges on each side to the top corner. Turn over the base and do it to the other side, too.
Step 6: Final Folds
fold in corners, etc. etc.
Step 7: Blow Up, Fill With Water