Every little counts, especially if you make it a routine part of your day.
Even on days that I can't get a workout in, I'll throw a few pull-ups in on my bar just for good measure. Sometimes I'll do half a workout. Sometimes I'll just do a quick set before I leave the house.
Every little bit helps. No excuses not to move your body for a minute per day. You'd be surprised how far it goes.
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I know what you mean about being in water. It's not nearly as strenuous as swimming, but if you're looking for some light cardio when the pool isn't an option then I've found that nothing beats a good creek hike. Get some waders on - or if you're feeling brave, just throw on some sandals - and take a brisk walk through the water. Be careful to avoid little piles of pebbles because those are likely carefully constructed fish nests.
In terms of exercise I can't imagine it's any more beneficial than a normal power walk, but the psychological benefit to spending time in water is worth it.