A few years back there was a clinical study on exercise benefits. The study found that even doing strreatches at your desk is beneficial.
Another part of the study showed that three 10 minute exercise sessions during the day helped to mainatin BG levels and gave incentive to not eat junk foods and actually you get more out of a series of short any type of exercises periods during teh day than cramming all of it into a 30-45 minute workout three times a week.
I fo on go snorkeling every afternoon if possible. and if not we do soemthing else, like biking or walking or something else
in any case a littlew all day long is better than skipping at all.