I did a bunch of 25's today, which I don't do very often, and almost every time I was faster by about one second going from the deep end to the shallow end of the 25 yd pool I swim in. I'm not a gifted swimmer by any means, but virtually every time leaving from the shallow end would net a time in the low 19:xx range and leaving from the deep end was in low 18:xx range. These were with a pretty quick 3-4 sec rest at around 90% effort. Any reason this would happen??

I think this was the first time I've swum 25's since I started wearing a watch to keep track of pool intervals - I'm assuming there was this discrepancy in the past, but I didn't notice it by just glancing up at the pace clock.