Started toying with the hot tub controls

[Originally by lolwritingcom]

Patrick had started to tell some kind of funny story about their trip there when Anne and Sophie returned to the hot tub, but Mackenzie could barely hear it, her heart pounding as the girls made straight for the controls of the hot tub. They probably didn't even know just how much they could humiliate her right now, but they weren't far from figuring it out.

"Boy, this looks like a real fancy hot tub! I can't wait to get to use it!" Sophie grinned. "You can set it to exactly the temperature you want and everything! Speaking of which, mind if I turn it up a few degrees, Mackenzie, since you'll be leaving soon?"

"Er... I mean, no, go ahead..." Mackenzie said sheepishly. What choice did she have? Maybe if she played along they'd go easy on her. The water started heating up noticeably- 'a few degrees' was apparently quite a lot, and it didn't help her arousal situation at all. Her head was starting to feel a little fuzzy, and she caught herself thrusting her hips gently, and stopped, hopefully before Anne and Sophie had seen. The jets had been teasing her for quite a while now- if she'd been alone she would have gone over the edge long ago.

"Look at all these buttons too!" Anne said happily, also grinning. "I wonder what... this one does?"

Anne pressed something on the control pad, and Mackenzie braced herself, as...