Hold Your Breath (Scene from Thoroughbreds)

A clip of two girls having a breath holding contest in a dark pool. One of them stays under for so long she starts drowning, but is saved by the other one. I found this video on Tumblr, but I'm not sure where it's from. I'm sure YouTube's content ID thing will pick up the source soon enough though. :D Update: Thanks to comments, we now know what movie this is from! It's from Thoroughbreds, a 2017 Comedy/Crime/Drama movie according to IMDB.