....and if so what can I do about it?

I have a cobbled-together setup that almost works. I coach swimming, and I
have a small video gadget that links to a Tivo and a TV via one of those
video transmitters that you can get from ebay. I think it is a 1.2 gHz
50mw version.

The kids swim and then watch, and having the Tivo means there's a
continuous flow of action. The problem is that the picture quality is bad.
I'm only 20 metres away and there is a direct line-of-sight from
transmitter to reciever - ocassionally with a body or two in the way; but
even without, there is considerable jumping and colour distortion and
generally a bad picture. If I stand still at just about any distance I can
find a place that gets a good picture, but moving - even turning - makes it
change.

The ceiling and the upper half of the inside walls of the pool are panelled
with strips of aluminium sheathing - about 6 inches wide and 20 or more
feet long. These are separated by about a 1-inch gap along the long edges,
and mounted to a framework (which is mounted to concrete) with some sort of
clip arrangement. This is a box about 220 feet long and 25 feet high.

What's the best guess for improving the picture? More power? Different
frequency? Antenna mounting (I could wear a beanie with it sticking up
from the top - that'd be cool)?