Whoa. Tried this, got all of ten feet--maybe. Between the isometric core to keep trunk vertical, plus the relative weakness of fluttering in this position, PLUS the huge resistance of your own back facing "forward".... yikes!!!
Just did my first swimplan workout, that was great! Keeps things interesting and moving along. The first plan was a little easy, but you can tell it to make things harder (or easier) next time, until you feel good about the level of difficulty.
Thanks for the tip!