Sister-in-law Exposure

My wife's family rented a cabin in the mountains for a long weekend. All of my in laws were there and, except for my MIL and FIL, all the adults and kids slept in the same large loft on the second floor. I was hopeful to get an opportunity to see my SIL naked but what actually happened may have been even better. My SIL is a sweet woman, about 5' 6", brown hair with a gorgeous body. She's very sexy but in a subtle way. Over the years, I've seen a boob here and there and even gotten a nice glipse of her pussy once while she was sitting on the floor wearing short shorts. I think she maybe flashed me on purpose but that could just be wishful thinking. She often shows off her cleavage and she always seems to look hot even when she's just wearing work out clothes of something casual. After the first day at the cabin, my fantasies were nowhere near coming true. Kids were running around everywhere and it seemed unlikely that she would be walking around in the nude or at least in something revealing. On our second day, we decided to go play in a nearby river. The adults helped all the kids get ready first and then they went outside to play while the adults got ready. In the loft, it was now just my SIL, my wife and myself who needed to get ready. In typical fashion, the sisters were talking up a storm while they were folding clothes and making up the beds. I needed to change into my swimsuit and was trying to be patient while they spoke to one another. I've always wanted to find a way to show my dick to my sister in law but never had the guts or much of an opportunity. With my wife in the room, I thought she might kill me if I got naked right infront of her sister. But I thought that this may also be my one chance. So without making a big deal about it, I took off my shorts (I was still wearing a t-shirt) and stood there naked as I grabbed my swim trunks. Of course I took my time. My wife and SIL just kept chatting but when I looked over at my SIL, her eyes were locked onto my cock. It was so exciting. My dick felt like it was on fire. I was in heaven. Unfortunately, I needed to put my swim trunks on before anyone thought I was intentionally flashing.  That whole day I was so aroused from that experience. I needed to leave to return home before everyone else so I had driven separately. Later that day as I drove home, I couldn't stop thinking about flashing my SIL and wondering what she thought about what she saw. I was so hard that I decided to masturbate in the car while I was driving. I don't think I have ever cum so hard in my entire life. Now whenever she gives me a hug, it seems tighter than it used to. I know I've fantisized about this experience many times. Do you think she does too or is that wishful thinking? Would love to hear your comments about flashing your sister-in-law.