Why is every ship a party adventure’s on in a TTRPG a three-mast sailing ship? While I only mean this in jest, I would love to hear of examples of adventures on other styles of ships that are accurate to the Middle Ages that inspired so many fantasy settings. But it seems that even in low fantasy, or historically inspired games and entertainment, other ship designs are sunk to the bottom of our collective memories.
The three-mast sailing ship is usually modeled from a Ship of the Line, typical warships from the Early Modern Era. These ships usually include one or more decks of cannons, fired in a broadside when parallel to another ship. But these ships, and their explosive armament, did not come into standard use for hundreds of years after the Medieval inspiration for many TTRPG’s. They probably get used most often because they look really, REALLY cool.
A ship that would fit correctly in the temporal space that we draw from would be the Dromo, a development of the trireme. These ships drew power from several masts, usually two or three, featuring lateen sails backed by a deck or two of oarsmen for added speed. The bow and stern of the ships could also be reinforced by large structures to hold heavy siege weapons. The prows also featured reinforcement with a casing of bronze or other metal to facilitate ramming. These ships were a common sight in the Mediterranean from Gibraltar to the Bosporus, from Genoa to Alexandria, and saw use by pretty much all the seafaring peoples during the Middle Ages.
If you prefer the large, multi mast sailing ships, the caravel was the grandfather of many Ships of the Line. Caravels added the lateen sails to a large hull capable of traversing the rough waters of the Atlantic. Many early European explorers used these ships for their travels, even though they are often shown in the more grandiose sailing ships.
It is totally fine to exclusively use the big Ships of the Line for your nautical-themed TTRPG if you want, but there are so many other types of ships, only a few of which I have discussed that would also be able to traverse the waves of your oceans. From longboats and triremes to dreadnoughts and battlecruisers, the sea is yours!