At the risk of sounding immature....this just doesn't sounds right.....:footinmouth:A little risky but it works....
Stick the vac part in the water. Put the other end in your mouth and suck until you notice the water moving along the tube on its own. Then place the end into your bucket.
It's obviously risky because if you are not careful enough you can end up with a mouthful of dirty tank water. The first time I tried this, I almost threw up from inhaling a bunch of salt water. :yuck: