The hot tub

Alice walked up to the hot tub, it was made of wood on the outside but was a nice smooth plastic inside, Alice pulled off her shirt and placed in on the floor next to the hot tub, she then lifted her left leg into it and followed with her right leg, she then sat down slowly and felt like she was in heaven! the bubbles were so nice on her sore muscles... Alice stayed like this for 20 minutes before noticing something...