to answer your
original question hippiedoll,
tub does not completely fill, it fills a bit of water in the bottom of the tub and then uses the impeller to hurl that water up and everywhere as the above videos show.
funny, when i saw my first ever dishwasher at my aunt's house in the early 60's i thought the tub filled completely up too! and this was a front loading hotpoint!
that would have made a great video if ya had to add a dish to the load!