[Full disclosure: I am a pure (i.e. "drop dead") sprinter ]
Watching Track & Field, I'm always struck how they offer what can truly be described as "pure" sprints: the 100m dash (and in indoors, the 60m). These are races that time sub-10 and sub-7 seconds at the elite level. Yet swimming's shortest race is 21 seconds (for the rest of us, quite a bit more than 21 seconds ...).
I was speaking with some sprint swimming coaches who agreed that even our "splash & dash" 50 free is not a true sprint ... it's close, but the best sprinters actually back off a tiny fraction from their absolute max to maintain a greater speed overall. At my USMS level, the winning times are in the low 25's. There's no way that's a true sprint -- 25 seconds is not entirely ATP-fueled. And while it's mostly anaerobic, is it entirely? Certainly a sub-10 or sub-7 race would be.
Time-wise, our 50 parallels Track & Field's 200 rather than their marquee sprint, the 100.
In my fantasy world, I imagine a 25m race at the international level (swimming through the finish like Track & Field athletes) ... fastest reaction, fastest acceleration, fastest underwater & surface, fastest ABSOLUTE speed.
Before 1988, our "shortest" Olympic race was the 100m!