DS5 got skipped!
No, not really. He got skipped in swim lessons. We weren't sure which one to enroll him in, but he WAS missing some key skills (back float, for instance) so we put him in a pretty easy level. Holy cow, did he ever improve. The swim instructor, young and a bit green, could NOT stop gushing about him all week long. ("He's the STAR! He's just INCREDIBLE!") She told me after the last lesson that he should definitely skip the next level, although they don't usually allow that.
The thing is, I don't think he's unusually skilled at swimming compared to other things. What he has that his sister doesn't has is the ability to use his smarts to immediately learn new physical skills, such that he just catches on to anything athletic very fast. The mind-body thing translates (I envy this; I don't have it.) He likes it all. Anything. Whatever. I still think of the time we went to a festival where they were selling (light, not heavy wooden) boomerangs. DS was 4 at the time and really wanted to try. The guy was like...sigh...okay (obviously humoring him). He showed DS the technique and how it worked and how to throw it, robotically. DS picked up the boomerang and did it perfectly the first time. I thought the dude was going to fall over.