You recall the fanciful illustrations of sailors blowing into the sail to
make waves. An inclined shaft with a small water propeller on the low
end, and a big air propeller on the other end, can achieve something
just as unlikely - it sails directly up wind.
And next, recalling that a released balloon shoots away from the
nozzle end, you may be surprised to see a balloon whose nozzle is
on top, and blowing onto an air propeller, which lifts the whole
contraption 20 ft or so
(At least in Arbor Scientific's embodiment)