This happened my freshman year of college with my then girlfriend. We both wanted to dive into the “college experience,” so we went out to some parties. Some big ragers, some smaller kickbacks. This story takes place during a smaller one, mostly just fast friends getting together to get drunk.
It was a Saturday, and the party started when the sun was still up. The house the hosts were living in had a pool and a hot tub, so of course there was a rule that you had to show up in a bikini.
The party started like any other, drinking, flirting with my girl, sneaking away (or not) to make out. The fun happened when the sun set, as it always goes.
Of course when it got colder we all crammed into the hot tub. 20+ people all jammed on top of each other, chatting, playing truth or dare, etc. My girl of course sat on my lap. Now I love to tease. I love the thrill of seeing what I can get away with. So I start “innocently” enough with having my hands on her thighs. She responds with grinding on me a little bit.