While we could invent a new ship, there’s little reason to, for several reasons. We aren’t likely to engineer something that would stay afloat if constructed, but a large variety of ship types are available to us already. Within each type, even more variety is to be found. This means we once again have leeway to make alterations of our own if we need to, provided we get the basics right. Naval terminology regarding ships was somewhat flexible at times, but settled into more definitive terms. This works to our advantage because we can get things approximately correct and fudge details for our uses. In addition, audiences seldom know much about existing ships and probably don’t thirst for something new. For these reasons, we’ll look at the more prominent, existing ships, not learn how to build new ones.
Vessels comes in two groups: long ships and round ships. The latter aren’t circular, of course, but are called this because they are wide when compared to the narrow and streamlined long ships like those used by Vikings.
The earliest vessels are the long ships, which are largely powered by oars but also have sails for additional propulsion. The galley is the primary type, and there are variations on it. All were designed for war or swift transportation, as opposed to carrying cargo.
Synonymous with Vikings but used elsewhere, the galley is the basic vessel powered by strong, highly trained rowers. It often includes a single mast and a metal-shod prow for ramming, an act followed by boarding. It is highly maneuverable but has a wide turning arc and requires calm weather. It is also not for open seas (despite being occasionally used this way) and is consequently found along coastlines. The invention and addition of firearms to ships caused this type to fall into disuse on Earth, but if our world doesn’t have gunpowder or similarly powered gunnery, the galley might still be favored.
The later, 17th century galley on Earth had two masts and a captain’s cabin at the rear, which adds usefulness to us as storytellers simply because a room exists in which conversations or acts not for others to witness may take place. If using this type of galley, we need another name for it, such as naming it after a sovereign power from which it’s thought to have originated.
The galley type known as a galleass is quite large, having both a rear and forecastle for artillery and soldiers, and up to twenty-five oars per side, each oar rowed by five men. Above the rower’s heads might be a deck for soldiers and operation of sails and gunnery. This ship wasn’t as fast and often served in the vanguard of an armada as a commander’s vessel.