I've been hoping @
Imaculata might chime in here with some notes from his pirates campaign?
Well, simulating naval combat in D&D is pretty difficult. Most of the game is designed towards a melee. For my
third edition pirate campaign I've been using the rules from the book
Stormwrack. But there currently isn't a 5th edition equivalent that provides rules for ships... and Stormwrack isn't perfect either, because it still tries to steer naval combat towards a boarding action as quickly as possible.
So we've had to come up with some house rules as well, and we're kind of figuring it all out as we go along. Last night in fact, was the first time me and my players actually played out a massive naval battle in D&D. We use miniature pirate ships from the game
Pirates of the Spanish Main.
But as you can see, distances and scale can be a bit of a problem. So here's what we did:
We first created
a large map, where each square represents
1/2 nautical mile. Stormwrack lists the speed of each ship in miles per hour. So for illustrating ship maneuvers, this works fine. But then as the ships close in to one another, ranges in feet start getting a little bit more important. For example, the players may want to snipe at the captain of the enemy ship from the crow's nest (something that was done in historical battles too). And perhaps the players want to exploit the range of their long range cannons, and stay out of range of the cannons of an enemy vessel.
This means that two captains have opposing goals, and they must roll dice to resolve a sailor check. Whoever wins, has
the advantage, and can determine the distance between those two ships. You can find more about the rules for maintaining and gaining the advantage in Stormwrack.
This is different from the advantage/disadvantage rules in fifth edition. They are two completely different things and not related at all.
But as mentioned above, once the ships close in on one another, you really need a zoomed in map. So what I did was, I created a simple map with squares on them, and told my players what the scale of each square was. For example, each square could represent 100 ft. or 50 ft., or even less. The point is, you don't want to do this zooming in too much. So it is best to pick a scale that works best given the amount of ships involved and their distances to one another.
Only one person can be the captain
Unless you give each player a ship of their own, you'll probably have only one player who takes the role of captain. And all the other players are stuck on the same ship with him. The total crew of a ship can easily count in the hundreds (mostly npc's), and you don't want to resolve hundreds of attack rolls. Because that would take forever. But you still want to give those players who are not the captain, something to do.
So here's what I did. I just narrated the gun fights between crews (I didn't play them out), and allowed the players to only focus on important characters on board enemy ships, such as the captain, or his cannon crew, or the ship's mage. I also allowed the party to take control of their npc followers (but not the entire crew).
The rest of the combat was focused mostly on exchanging cannon fire, and moving ships. I gave each player control of an allied ship, so they could have just as much fun. They got to roll damage for the cannons of 'their ship' (the ship of an ally that they controlled), while their PC was still on the main player ship. The players were of course free to discuss tactics, but each player would control only one ship during their turn.
So each player basically does on his turn:
Ship movement -> Ship actions -> PC actions
(A ship's action could be firing its cannons, reloading, extinguishing fires, or anything else.)
So, by doing this you have the benefit of allowing all players to take part in the battle (even if their PC is sometimes out of range of any enemies), and you simplify the naval battle to mostly firing cannons. But you don't ignore the obvious advantage that individual PC actions, such as spells, can have in a battle at sea. But be aware that you should also give your bad guys a mage on board their vessel to deal with the menace of magic at sea. Yes, it is a menace!
The boarding action
Eventually though, for D&D it is probably best to steer towards a boarding action. In historic naval battles of the 16th century, ships would often use sail-hunting tactics. They would try and take out the rigging of an enemy ship, which would put it dead in the water. And Stormwrack seems designed with this in mind. It is quicker to take out a ship's mast, than it is to sink it. And since Stormwrack doesn't have rules for accidentally hitting a ship's gunpowder room, instant victories simply don't happen. It can take a long while before you actually destroy some of the bigger ships through damage alone. And so, for D&D you probably want to
prepare a map of both the player-ship and the enemy-ship.
Besides, it is fun to play out battles on board ships. There's an excellent map pack from
Game Mastery, which is very useful for constructing ship maps. It has small maps for sections of ships, allowing you to assemble them into a ship of nearly any size. It is pretty easy to get a hold of, I've seen it in a lot of game stores. And if they don't have it in stock, you can always ask if they can order it for you. And you can of course also make your own maps.
Range and siege weapons
So this is where we abandon reality. Ranged combat in D&D has never been realistic. It doesn't try to be, because if it did, why go into close combat at all? So for that purpose, ranged weapons in D&D tend to have a far shorter range than they would in real life. This design decision does however have some side effects. When you add modern weapons such as guns and cannons into your D&D, you're adding weapons that have insanely long ranges. So what they did in third edition, is cut most of the real life ranges in half. And this is what we also did for our pirate weapons. In my campaign setting, cannons tend to have a range of about 500 ft. This is not realistic. Any real cannon could easily hit twice that distance. But you have to make it work with D&D's combat system. This applies to both third and 5th edition. You most likely don't want to use realistic ranges, because it completely undermines everything else in the combat system, such as spell range, and bow range. Concessions have to be made.
Ships, sections, riggings and hardness
Stormwrack does not include cannons. It assumes a classic medieval fantasy setting, and so it assumes that ships may be equipped with catapults and ballistas. The idea is that each ship has a number of hull sections. Each hull section has a hardness and hit points. If a hull section is reduced to 0 hit points, it is holed, and water starts pouring in. The ship's captain must immediately make
a sinking check (See Stormwrack), and if adjacent hull sections are at 50% of their hit points, they are immediately flooded as well. At a certain number of holed sections, the ship sinks immediately.
The bigger the ship, the more hull sections it has, and the more sections need to be holed in order for it to sink immediately. Bigger ships also have more rigging sections. If you take out a ship's rigging, it is dead in the water, and isn't going anywhere. If you take out half a ship's rigging, it's speed is halved as well.
But remember the lack of cannons in Stormwrack that I mentioned earlier? In real life, pirates often used special ammo to specifically take out rigging. So in order to simulate this, I house ruled that pirates in my campaign can use this type of ammo (such as ball and chain), to deal double damage to ship's rigging. You won't find this in any D&D books, it is a house rule.
Ship upgrades
One of the things that I immediately added, was lots of stuff for my players to waste their gold on. Since my players play pirates, they'll be making a ton of money easily, and they want to spend it. Ship upgrades are minor improvements to a ship's performance, that cost a lot of money. Some are a single purchase, such as a magical figurehead, stunsails, a davit, a better cannon, improved rudder tackle, etc. Others have to be applied per hull section, or per rigging section, such as copper sheathing, silk lines, vinegar coated sails, etc.
Stormwrack provides various statistics for ships, all of which theoretically can be improved with upgrades. Such as movement speed, shiphandling, sea worthiness rating, firing range, section hp, section hardness, rigging hp and rigging hardness.
Stormwrack does not provide ship upgrades, so we made lots of upgrades up ourselves. The players can add upgrades that provide fire resistance to parts of their ship. They can add an extra firing castle to the ship. Heck, they can even add a glass bottom to their vessel if they want. Or what about a diving clock, and diving suits?
All of these minor things are fun for your players to work on. And once they are done upgrading, it is time to move on to a new bigger ship that they can waste even more gold on!
Tactics and commander rewards
Me and my group are kind of making most of this up as we go along. We've moved way beyond Stormwrack, and introduced tons of things that aren't in any books. Stormwrack serves as a basis that we build upon. One thing that I'm about to add, is something I read in the mass combat rules of Pathfinder. The idea is that whenever the players achieve victory in a big battle, they learn a new tactic. Usually this will be a tactic that relates to something they did during the battle itself. This tactic can then be issued as a command to other ships/units in the player's fleet/army. So each big battle, comes with its own commander reward.
I have yet to start work on this list, but I'll update my campaign topic when its done.
