If you feel you over-did little bit this mornings run then I recommend you do very low intensity swim tomorrow. To me any water activity - swim, whirlpool or hot-tub - is like very light massage that helps recover faster from hard workouts. However - you know yourself and your body better then me. Stick to your plan if you feel that is the best.
I was planning to join this morning for a run - I had my work clothes strategically arranged so I can take shower and get dressed in no time after the run, I had my running clothes and shoes arranged so when I get up I am ready to roll. However I could not force myself to fall asleep on time - up to the point that I got up and was working on my Emails. I think it was about 1AM last time I was looking at alarm.