Anybody else see movement from the outside?

So today I'm 13w1d. Tonight I was standing around waiting to get in my friend's car, and I looked down, and I was lopsided! My belly was bigger on the left side than the right. And as I was staring, I swear I saw some weird wavey movement that I know I can't do with my abs. But, I still haven't felt the baby from the inside yet. Is that even possible? Has that happened to anybody else? Btw, it was the weirdest and coolest thing ever.