i voted up the name, not the swimmer. I want my vote back!

Stars for the name.

I swam competitively for about 15 years, and I'm pretty sure it does. One of the events I always got stuck with was 500M Free, and I'd usually take a "backstroke break" somewhere around 200M for a length or so, since Backstroke is for most the fastest (butterfly's potentially faster but not recommended especially for long races) to conserve energy and nobody said anything.. the most common are the big 4 of course but as far as I know you can do whatever crazy stroke you want as long as you come up to the surface within (I think) 10 meters of the start or wall-turn.

And doing a butterfly kick with the backstroke is pretty common, and this particular position happens on nearly every flip-turn, since post-flip you're not yet in the backstroke position. Maybe the rules have changed since the mid-'00s, but that's how I remember it.

Zest is right, there is a rule that you have to come up to the surface within a finite distance. This particular stroke (also called the dolphin kick) is actually the fastest way for a human to swim, but it requires you to stay underwater the whole time. So swimmers usually do the maximum allowed amount after a turn before coming up and switching to a surface stroke.

So it's "anything goes" except for a specific rule that prevents this style from being useful for the whole race.

>>I swam competitively for about 15 years.

You have worn many hats, and for that, I tip my hat. At your hats. Hats off.