Seems like that'd be 20 miles or so, right? Sure, it is possible*. People paddle 50 miles at a whack. But, they are not ordinary paddlers. Just make sure you are up to the distance, or 1.5 times the distance in case it is tough going.
The asterisk is because I'm not sure if you'd be allowed paddling the C&D canal. That should be easy enough to look up. Be aware, the current rips through the C&D. I'm guessing it is tidal, and if so, you should catch it going the right direction.
There's a state park with camping at Elk Neck. I think you'd be wise to plan to overnight it there. While twenty miles doesn't seem that far, if wind and tide conspired against you, it would be very tiring. If you planned your stop right, it would give you time to await a favorable tide.
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