What made us challenge each other I cannot remember, but once you have agreed a challenge you have to go through with it. Jen and I had been friends for about 10 years. All through school we had been very close. We shared everything but were never physically involved with each other. We had gone off to different universities but went home for the summer holidays.
So there we were early on a Saturday afternoon during the holidays sitting by the small swimming pool at my home. The pitchers of water in front of us were identical and we had had our last visit to the toilets. We had got into a silly discussion about how strong our bladders were. The challenge was meant to establish who had the strongest one. To start things off we both had to drink two liters in 15 minutes, which presented no problems. We had agreed to be naked from the waist down so that there could be no cheating. Neither of us had been in the slightest bit interested in the lesbian going on amongst our friends but seeing each other naked was commonplace.
Things were going slowly and we agreed to speed things up by drinking identical glasses of water. Very quickly my bladder was full but not too uncomfortable. It was a warm afternoon and we both decided that complete nudity was more comfortable, so stripped our tops and bras off. We were sitting on the edge of separate sunbeds facing each other until we began to feel fuller. We then moved so that we could prop ourselves up but lie back more comfortably.
It took much longer than I had expected for us to get to the stage when things became really challenging. It was at this stage that I was surprised to see that my nipples had become painfully erect even though I was warm. Looking across to Jen I discovered that hers were the same. I commented about mine and she casually stroked her nipples making the areola shrink and her nipples appear to grow bigger. Fascinated I copied with similar if less spectacular results.