I'm not focusing on rules here, but more the style of play and amount of decisions required. Based on this example of play, do you think you'd be interested in these rules if you ran naval scenario?
(If I published this, I'd include some mock-ups of a map of the environment, to help understand how the ships move relative to each other.)
[h=4]Play Example[/h]The PCs are seeking a dungeon that’s supposed to lie somewhere along a river that cuts through a rainforest. Monsoon storms have overflown the banks, and now the water level is halfway to the forest’s canopy. Their schooner, On Silver Sails, has five cannons per broadside, and enchantments on its sails provide it great speed and maneuverability.
The PCs spot a warship, the Nergal, 2000 feet upstream, heading their way. The PCs’ cleric has heard of this ship of the damned. He warns that the Nergal’s topsail bears an enchanted weapon – a clawed star woven into the fabric, crackling with unholy fire – and its gun decks carry a total of fifteen cannons per side.
The PCs know they could flee and outrun the Nergal, but they need to deal with it if they want to explore for the dungeon. The captain orders battle stations, and combat begins.
Round One
The PCs decide they’ll weave through the flooded woods, trying to stay in cover as they close the distance. The wizard will pilot, the fighter acts as lookout to help navigate, and the cleric inspires the sixteen crew members to work harder and try increase the ship’s speed. The captain (a rogue) directs the crew to go about their tasks quietly, and even orders a few sailors to make a big show of setting up useless rigging, all in a bid to hide their intentions.
The two captains roll initiative, and thanks to the PC captain’s gambit, the Nergal fails and has to act first.
The Nergal’s base speed is only 6 (meaning it moves 600 feet in a minute, or about 6 knots). To represent the actions of the vessel’s officers, the GM chooses one simple set of orders for the ship, in this case the ‘Heave To’ order, which slows the ship to speed 3 so its cannons have more time to aim. The ship advances a leisurely 300 feet, turning slightly in the middle of the river to bring its broadside to face the party’s ship downstream.
On Silver Sails has a base speed of 8. The wizard pilot makes an initial piloting check and manages to coax a little extra speed, and with the aid from the cleric’s inspirations the crew up the ship's speed to 10. But once they sail into the forest, they’re in difficult terrain, so the ship advances slowly. One patch of forest is particularly dense, forcing the wizard to make another piloting check, and despite the fighter acting as lookout he fails. The ship becomes caught!
After the Piloting stage, the two ships are 1200 feet away, long range for their cannons, but out of range of the Nergal’s deadly flaming brand. The forest between them grants each side cover, but On Silver Sails is heading on a course that keeps its cannons from firing back.
The Nergal unleashes a barrage of fifteen cannons. With the disadvantage from range, the bonus from ‘heaving to,’ and the cover of the trees, five shots hit, dealing 200 damage out of the ship’s 610 HP total. The NPC crew makes a Dexterity save to avoid exploding splinters and being hit directly by cannonfire, but they fail and so take 20 damage out of their shared HP total of 80.
Round Two
The captain concludes that his initial strategy was an unmitigated disaster, but the urgent concern now is getting unstuck from the forest.
Again, the two captains make initiative checks, and On Silver Sails loses. The fighter directs efforts to get the ship unstuck, mostly relying on brute strength to shove the ship away from trees. The cleric tries to get injured crew back on their feet, and he manages to heal the damage the crew took last turn. The wizard pilot has an idea he thinks will save them, and so the captain takes the ship’s wheel. The ship manages to break free, and the captain winces as he scrapes his way roughly through the forest, steering his vessel 400 feet closer to the Nergal but staying at the edge of the forest.
The Nergal wants to close for the kill, but normally it takes a round to reload cannons, so it chooses the ‘Fire at Will’ order, letting it fire five of its cannons right away. It corrects its course down the flooded river, coming within 300 feet, within close range for its cannons and the supernatural weapon on its topsail.
That’s just close enough for the PC wizard’s trick. He casts control water and creates a whirlpool beneath the Nergal right as it’s about to open fire. The enemy pilot has to make a piloting check with disadvantage, but fails, and the ship is spun in the direction of the wizard’s choice. The infernal galleon’s broadsides rotates away, ruining its chance for a destructive barrage, and exposing the ship’s aft. On Silver Sails fires its own cannonade, and at point-blank range three of the five cannons strike true, dealing 120 damage to the Nergal (out of 800 HP). The infernal crew succeed their saving throw, and so only take half damage – 6 HP from their pool of 160.
The Nergal’s doesn’t fire its broadside, but its topsail brand can tack in any direction, and it flares like a golden beacon above the swollen river. A beam of hellfire cuts across the water, boiling up steam as it tracks toward On Silver Sails, but the attack narrowly misses, instead setting part of the forest ablaze.
From three hundred feet away, the party sees the enemy captain, clad in a black coat with rusted iron trim, smile with dry amusement, then give an order. As well as the PCs can read lips, they think he said, “Kill their wizard.” For a moment it seems like the entire crew of the infernal galleon has a five-talon fiery nimbus floating behind their heads, like a hellish halo. The PCs suspect attempting to board would be a fight they couldn’t win.
Round Three
The PCs know they need to pepper the Nergal with cannonfire to soften its crew, while staying out of the path of its broadside. Toward that end, the wizard pilots again, and the cleric shouts for the crew to help the wizard with the risky maneuvers he’s going to be pulling. The captain corrals the gunnery crew and tells them to focus fire on clusters of enemy crew, which speeds up reloading and grants the fighter advantage on his attack roll with the cannon battery.
The PCs win the initiative, so the Nergal is forced to move first.
It has to been spun in the wrong direction by the wizard’s whirlpool, so it will be hard to avoid crashing into the forest. It would make sense for him to give the ‘Full Sail’ order, but the captain nevertheless chooses ‘Heave To,’ to make the ship’s aim easier. The galleon navigates out of the whirlpool and cuts a clumsy wide turn across the river. On Silver Sails, meanwhile, keep its speed high enough for it to sweep in behind the infernal galleon and level a broadside from 400 feet away - close range for its cannons, but long range for the brand.
During the gunnery stage, the Nergal aims its fiery brand backward at the PCs’ ship, focusing on the wizard’s location, and despite it being at long range, the burning beam hits. It deals 200 damage just by itself, and On Silver Sails namesake sails have caught on fire. The strike also cuts a swath across the deck, incising black talon-shaped burns into the wood and dealing 20 damage to the crew. The wizard also takes 20 damage, since he was specifically targeted.
Now it’s the fighter’s turn, and he times the cannon volley to strike clusters of enemy crew, using one of his class abilities to boost his attack roll. All five cannonballs land solid hits, but because he decided to aim at crew the shots do half damage to the ship – only 100 HP instead of 200 – and do double damage to the crew – 40 HP instead of 20.
Cursed sailors of the black galleon are blasted overboard or flee for cover despite their captain’s threats. A few more passes like that and the party might be able to board the ship and force a surrender, but the PCs will need to deal with the fire before it spreads and cripples their ship.
