further to this topic I wonder if the temperature of the water is
an important factor or whether it's salt or fresh water. Perhaps
the star sign of the swimmer and researcher (maybe) is important.
what about the rope or harness doing the tethering - could the
materials used be of consequence?
Then again there is the direction of the swimming and the degree of
alignment with the earthlines in the area.

In recent work at our lab with trying to teach starlings to fly
underwater we found limited success with our work and the debate
on tethered swimming has sent us back to the wading pool with a
host of new ideas. Our results will be published in a forthcoming

Cook, P., Moore, D. and Gnomes, Lord, 1995. Underwater avian flight
: A review of the literature and preliminary findings from an
exploratory pilot programme using the Siberian starling
J. Irreproducible Results, Vol. XXI, No 24, p223 - 223.