Depends on alert or unconscious
For an alert casualty, we used to use cross chest tow (hand under boob), for an unconscious casualty, an extended tow. When you start, you learn to save unconscious people as they struggle less and are less likely to drown you, like conscious casualties are prone to do (especially if you're grabbing their boobies)
(lardyboy Next stop, Fissplap Central, Tue 11 May 2010, 14:02, 1 reply)

What if they're dead
and you want to bring them back to shore for a dignified burial? What method would expend the least energy? I'm guessing you'd just do a sort of side-stroke, pulling them along by the hair?
(Happybara The jungle came alive and took him, Wed 12 May 2010, 10:03, closed)

hold them underwater
...between your thighs. Then do some sort of breast stroke (no pun intended) or back stroke. That way you'll have both of your arms free
(Tilde, Wed 12 May 2010, 16:07, closed)

But my arms are weaker than my legs.
Surely it would be best to leave the legs free? Also if you're doing (ooer, missus!) breast-stroke then your head is high enough out of the water that people will be able to see you crying.
(Happybara The jungle came alive and took him, Thu 13 May 2010, 11:09, closed)

If it was this same girl,
I would sit astride her and ride her like a surfboard.
( Blind Meach Cautiously optimistic, Wed 12 May 2010, 17:33, closed)