I made these guys about 2 years ago after seeing an article in Family Fun magazine. It is made out of 3 sponges (the cheap ones are GREAT for this) just cut in 1 in lengths (you get 5 out of one sponge - you need 15 "fingers" all together) once you have them cut up you lay them down 5 at a time (in whatever order you want) stacking them up 3 high - you can either tie with a peice of string (which this one shows - or what we found works better (after one peice of string didn't withstand the torture it was being put under) a covered hair elastic!
My son loves these.
They work great in the water and actually get you pretty wet when they hit you! Let them dry completely before you put them away until their next use!