Her top.

"Hand over your top and I'll turn on the bubbles." Sienna demanded with her arms crossed, she was looking kinda scary with how dominant she was...

"But people will see my tits!" Alice complained.

"No they won't, just duck down and the bubbles will hide you."

"Assuming you keep your end of the bargain..." Alice responded unsure.

"You can trust me Alice, buuut if you don't want to... we can leave it off." Sienna said finally.

"No! OK OK its coming off..." Alice said defeated, she squeezed her legs tightly shit before removing her hands to undo her top, once it was off she kept a hand over her breasts while using the other to throw her top at Alice, she was now butt naked in the hot tub!

"Oh my god you did it!" Sienna yelled.

"Yes now turn on the bubbles!" Alice demanded red faced.