It is actually gunwale rather than gunwhale which some contract to "gunnel".
A wale was a term used for a plank or board and a gun wale was a platform used to mount guns on the side of an open boat or deck of a ship.
The closest thing to a gunwale on a conventional kayak would be the structural element surrounding the open cockpit, but that is called the coaming.
Some kayaks have a gunwale like strip of wood running along the seam between the deck and the hull, but that is typically called a rub rail.
Recreational Kayak Paddle