If you're running low on TP, be thankful you still have some, and don't have to use an old sailor's method. The always interesting Old Salt Blog reports:
Sailors in the Age of Sail used tow-rags. What is a tow-rag? As can be seen in the video below, close to the ship’s head — the toilets in the bow or “head” of the ship — there was a long rope ending in a short rag that hung over the side into the water. After using the head, the sailor could then clean his backside with the wet rag then drop the rope back over the side. The rag would then be cleaned either by being literally towed by the ship under sail or to be washed by the action of wave and current if at anchor.
The word “tow” may refer to the process of the rope being towed underway but is more likely to be the type of hemp woven rag used at the end of the rope, referred to, even today, as tow.
There's more at the link.
The report also offers this video clip, showing the heads and tow-rag aboard a modern replica of the 17th-century Dutch sailing ship Batavia.
I'm glad I was never subjected to that during my (relatively few) seagoing days!