Agreed. Wasn't track barefoot back in the day? I mean even shoes are an advantage. Swimming sped up after goggles and swimcaps were accepted. I think it's all just where do you decide to draw the line? I've thought badminton is an odd sport, the shuttlecock is so slow anyone can (normally) play it - it's very inefficient. And don't get me started on equestrian if grandpa can win it then shouldn't the horse get the medal?

Finswimming is actually a separate sport, just not an olympic sport. Although it has some exciting characteristics like very fast 50 meter races, which I enjoy as a "regular" (non-fins) swimmer.

No, if efficiency can be used to evaluate if a sport is legit, only cycling should be allowed. No running or swimming. The point is that efficiency is an asinine ground to judge a sport on.