Notice "hinge" affairs on gunwale deck edge [also spelled gunnel - see below], close to railing stanchions. That makes sure it must fold upward toward boat. Those hinge affairs as well as the rest of the unit seem to show it is not a just diy unit; but rather, a purposefully manufactured item??
Therefore... potential bath unit for a baby??? - soooo... boat owner does not "throw baby out with the bath water"
Interestingly:
"Gunwale" is defined in the dictionary as the uppermost edge of a ship's side. That word originated in the late 15th century, when a "wale" was the name for a plank on a boat. ... The original spelling in Old English was "gonne walles", or literally "gun walls", because it was the wall of a ship used to mount a gun.