How could I forget this one?..
I was at a Holiday Inn in Colorado on a ski trip with my dad. We had just arrived, but were not skiing yet as it was in the afternoon. He and I went to the pool area and started soaking in one of the two hot tubs.
Ok, that part's not sexual, but this next part is, and it doesn't involve Dad at all --
The other hot tub was around the corner from some dividers, so we couldn't see much of anyone in it. What we didn't see until she got up to restart that tub's bubble timer was a very attractive, nicely-built girl who was wearing a yellow one-piece tank swimsuit that was almost completely sheer.
I couldn't believe it. Here was this model-quality babe, striding across the pool deck, with perfectly shaped B-cup breasts with silver dollar-sized nipples and a modestly trimmed bush all showing proudly through the soaking wet, sheer yellow material. It was exactly the kind of image that I'd later see all over the internet on softcore sexy bikini sites. And here it was, right in front of me, in the middle of the afternoon, with no party scene, no flashing lights or smoke machines -- nothing that would get me into a frame of mind for viewing a sexual exhibition.
I watched her walk back, and was so immediately horny that I started playing with myself right there under the water. After a couple minutes, I stopped, but soon excused myself and went to the sauna overlooking the pool area. It was inoperative, but I didn't care, because I needed some privacy while I jerked off.
I've never wanted to fuck a total stranger's brains out as much before or since. Sheer swimwear remains a huge turnon for me.