Because we rent out cottages, we also have fishing boats that we rent out to folks who need them. Nothing fancy, just 14 ft aluminum boats with 9.9 motors. Back when I was younger, one of my many jobs was cleaning them before they were taken out.
I've found everything and anything cleaning them out, usually in at least at least a few inches of dirty, rank liquid. From the mundane including entire containers of live bait, be it worms, leeches and helgramites (nasty things) dumped on the floor for easier access, barbed hooks, and live fish just caught and left to die, to the disgusting such as wet socks, human shit, and shit-in underwear. Nothing worse than using your big sponge to soak up said rank liquid, only to get to the middle of the boat, find a turd, and realize the liquid you had your bare hands in was part log.
The shit-in underwear occurs frequently enough that I can only assume, the dudes renting found what they considered to be an awesome fishing spot and refused to leave it.
I've since passed the boat-cleaning torch to a younger hireling. Wehehehee. Stay strong, T234.