Negative Split in the Pool

Today was a first! Got my first negative split in the pool during my lunchtime swim. First 400 meters = 10:53, second 400 meters = 10:47! I'm not sure how it happened. I wasn't trying to do it. Although I've been trying to start more conservatively and finish stronger, I wasn't making it a point to neg split, but it happened. I'll take it! These half mile swims at lunch are finally making me feel like I'm improving.