I have been kayaking Pleasant Bay / Little Pleasant Bay for years. One of my favorite spots to take a break is the northern tip of Sampson Island. As shown in one of the attached pictures, the island is open to the public. Directly off of its northern shore are multiple oyster breeding grounds. The tides move the pristine water of the bay over the shellfish, creating delectable snacks. At high water you can kayak right over them. Look but don't touch.
There is generally always a channnel for boat access but if you try to paddle up the east side of the island (highly recommended) you will likely run out of water at low tide. A number of different put-in locations are contained in the link below; the closest is the Orleans town landing at PawWah pond. As always you need to be aware of the tides. Pleasant Bay can also get very windy, kicking up considerable chop.
This is a medium-sized tupperware container with only a small log book and pencil. I placed it above the high tide mark and looped it around a tree. Time will tell if it survives the elements. Sorry, no FTF prize other than the satisfaction of doing so.
http://capecodtidings.com/orleans-kayaking-guide/