Lots of great stuff happening on HBO tonight. Who knew?
Vulture has a big piece on this scene, which includes this reaction from Allison Williams's dad, Brian Williams:
She's always been an actress. For us, watching her is the family occupation and everybody has to remember it's acting, no animals were harmed during the filming, and ideally nobody gets hurt.
And here's how Allison described the making of this scene to Entertainment Weekly:
I had a couple of days talking to wardrobe and makeup to get ready to rig the thing that I wore for the ass motorboating. It was an engineering achievement! I would manufacture it if more than one person a year needed it. [Laughs] It was so elaborate—it involved Spanx that we cut away and glued down and involved menstrual pads and two of those weird thongs. I've had to do scenes like this twice now.