Step 1: Buy (if You Don't Already Own) A Nerf Super Soaker Hydro Cannon
Step 2: PVC
Buy some PVC piping. I think it is a half inch. Whatever snugly fits a nerf dart. You just need one that fits into the gun itself.
Step 3: Connectors
Buy male and female screw on connectors.
Step 4: Glue
Glue which ever connector is the shortest to the barrel. This will allow you to use nerf and water mode.
Step 5: Barrels
Now it's time to make your barrels. Cut the PVC pipe to whichever length you want. The airsoft should be roughly the length of a ballpoint pen. Now attach each connector to one side oculus barrels.
Step 6: Airsoft Barrel
To make the airsoft barrel, gut a ballpoint pen so you just have the tube. Wrap the ballpoint pen tub in sticky tac or putty.nstick that in your shortest barrel so it fits snugly. Make sure NO air can escape when firing.
Step 7: Customize
Paint your gun or make it look cooler
Step 8: Connect
Screw the connectors together so that one barrel is attached to the gun. DO NOT screw them together all the way. That's it! Have fun shooting!