What you need:
water bottle with cap
aluminum can or other metals you can cut
motor (one that spins fast?)
tubing (copper or other source...)
power source (3 - 9 volts)
hot glue gun
Step 1: Prepare the bottle cap
Drill a hole in the middle of the bottle cap making sure its centered about the same size of the middle of the motor so it fits in. Drill a hole in the side big enough for the tubing going out. Don't forget to drill a hole in the bottle cap so the tubing can flow out.
Step 2: Motor and impeller
Hot Glue your motor onto the bottle cap and make sure it spins by hooking it up to a power supply. (It doesn't need to be water proof...) If you haven't screwed the neck off yet do so now. (It'll make things a lot easier.) Hot glue your impeller to your motors shaft and let it cool. Screw your bottles neck back on and your done with this step..
Step 3: Plexiglas and power
Glue the output tube to the side making sure that doesn't interfere with the impeller and you're done....
Connect to a 3 - 9 volt power supply and submerge it underwater and watch it flow!
Step 4: Final thoughts...
I have a slow motor from a ps2 controller and lets say it doesn't work too well...
Also just to tell you all, this only works under water. so make a long cord attaching to the battery, and don't leave it in the water too long or it will rust and not work anymore..
Questions you may ask.
Q. It doesn't work!
A. is the motor working? impeller stuck?
Q. It doesn't go as high as i thought.
A. are you under powering it? try 6v or 9v..
Q. why would i need this?
A. you can use it to pump water for computer water cooling or anything you want.