Naval Combat rules

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The rules for naval combat are largely based on The Complete guide to Nautical Campaigns by How to be a Great Game Master. This page summarizes the system from a player’s perspective, and some details may be abbreviated or simplified. In case of conflict the rules as written in the Complete Guide take precedence.

There are two types of naval combat described in the rules:

Boarding is essentially the same as regular combat, with a few additions, so most of this page will focus on Chase Combat.

Ship statistics

Each ship has its own statistics that are used in various situations including combat. I will briefly list them here as they referenced in various rules, but for the full explanation please refer to the Complete Guide.

Statistic Use
Crew capacity Determines the number of crewmembers a ship can have. Stat blocks typically list a starting number and a maximum capacity
Crew quality (CQ) Represents the training and experience of the crew. Used as a modifier in many checks
Cargo capacity How much cargo a ship can carry
Ship size (SZ) A modifier that represents the size of the ship, and is used in various checks to modify the DC
Travel pace The number of miles the ship crosses in a typical day of sailing
Strength How much strength a ship has as a result of its movement / propulsion
Dexterity The ship’s maneuverability
Constitution Structural soundness of the ship
Charisma Visual impact of the ship to observers. High charisma represents extreme beauty or extreme horror
Stores Ship resources. Categories include: food, drink, medical, supplies, and various sorts of ammo
Replacement cost The cost to replace a store
Salaries How much the crew needs to be paid (total)
Orders How many orders the crew can execute in a single turn

Chase combat

Chase combat is what happens when a hostile ship comes within range (within 800ft for regular ships, 200ft when underwater) of its quarry. Chase combat can end in a number of ways:

Movement

Rather than using a grid with exact positions, naval combat uses a distance tracker with relative positions.

Surface tracker Underwater tracker
Surface tracker Underwater tracker

At the end of each turn, the movement speeds of both ships are compared:

Speed difference Movement effect
Target ship > Chasing ship (factor 2 or more) Target ship moves two positions to the right
Target ship > Chasing ship (less than factor 2) Target ship moves one position to the right
Equal speeds Target ship remains in position
Chasing ship > Target ship (less than factor 2) Target ship moves one position to the left
Chasing ship > Target ship(factor 2 or more) Target ship moves two positions to the left

Officers

A ship is run by its officers. These officers can be both PCs and NPCs. A ship can have the following officers:

Officer Task Relevant stats
Captain Leads the ship, manages its operation Wisdom, Charisma
First Mate Link between crew and captain, ensures smooth operation of ship and responsible for morale Wisdom, Charisma
Bosun Ensures the ship’s structural integrity, layout. Basically a chief engineer Strength
Ship’s Mage Magical liaison between the ship and the ocean, using magic to get the ship where it needs to be Intelligence, Charisma
Quartermaster Ensures the ship is well-supplied; responsible for navigation Wisdom, Charisma
Surgeon Keeps the crew healthy, interrogates prisoners Intelligence, Wisdom

Turns

Ships cannot take actions on their own, so their actions are determined by their crews. As crews can get quite large, the initiative order only tracks any officers a ship may have, and all players.

On each turn, a player can take actions as they normally would, and if they have the role of an officer aboard the ship in question, issue a command (this is generally a free actions, unless stated otherwise). Some of these commands can be issued out of combat as well.

Orders

Officers can make the following orders for the crew to complete. Not all of these orders are combat-related.

Order Type Issued by Effect
Fire! Attack Any officer All weapons that belong to a single weapon component fire on the target vessel, targeting their hull
Brace! Buff Any officer DC12 CQ check. Reduce all non-magical damage to crew by 2D10 for one round
Training Buff Any officer Takes 3 days to complete. Crew trained in hand-to hand combat an hour daily, increases CQ by 1
Learning Buff Any officer Takes 3 days to complete. Crew trained in seamanship an hour daily, increases CQ by 1
Get us moving! Movement Any officer When ship has speed 0. Ship speed is 10ft this turn, and regular speed next turn
Put that out! Repair Any officer DC5 CQ check to put out a fire. May take multiple orders to complete if larger fire (up to 4 orders)
Focus fire Attack Captain or First Mate Single weapon from a weapon component attacks with advantage, targeting their hull
Reload! Attack Captain or First Mate Requires an extra officer (any) near weapon. Allows a weapon component to make a second attack
Split your targets Attack Captain or First Mate Attack multiple targets with single weapon component (if component has that many weapons). Targets hull
Sacrifice to the gods Attack Captain or First Mate Sacrifice two crew members (-1 CQ) for kamikaze attack using rowboat against enemy hull within 200ft (CQ vs AC). 8D10 Fire Damage + large fire started. Crew members can be retrieved after combat on miss
Kill them all Attack Captain or First Mate Attack vs enemy crew within 100ft. Attack vs Helm AC. Kills 2D6 crew on hit
Launch: attack target Attack Captain or First Mate Launches naval or aerial units from the ship to attack target ship
Rip it open Attack Captain or First Mate Requires harpoon embedded in target. Strength vs. DC5 + Target ship size. 2D10 damage to target per harpoon on hit. 2D10 damage to harpoon component on miss
Drag it down Attack Captain or First Mate Requires harpoon embedded in target Opposed ship Strength check. On success both ships reduce speed by 40ft per round. Failed check 2D10 damage to harpoon component
Ram them Attack Captain or First Mate Requires 50ft distance or less. CQ check vs target hull AC. 16D10 damage to target. Ramming ship makes Strength DC5 + target ship size check. Half that damage on success, full damage on failure. Target speed reduced by 20, ramming ship speed reduced to 0. Both crews 1D10 casualties.
Evasive Buff Captain DC14 Insight check to gain +2AC to all ship components. Disadvantage on all attack rolls. Lasts until officer’s next turn
Hide Buff Captain or First Mate (ranking) DC10+SZ Survival check to be removed from combat for 1D6 rounds. Requires suitable hiding spot nearby. Surface ships cannot hide from aquatic ships unless in a storm
Hoist the colors Buff Captain or First Mate Raise flags to send a message. Other ships require DC14 Insight to determine if message is true or a ruse. If ship raising flags has Charisma of 14 or greater, it has no effect as its reputation preceeds it
Club hauling Movement Captain or First Mate 180 degree turn using anchor. Requires DC5+SZ Dexterity check, ship takes 2D10 Hull Damage
Dead stop Movement Captain or First Mate Drop anchors to stop. 1D10 points of hull damage per 10 feet of movement speed. PCs must succeed DC14 Acrobatics check or be knocked prone and suffer 1D6 damage. DC14 CQ check, lose 1D4 crew on failure. Attackers get disadavantage on attack rolls, but gain 3 range increments unless they also did a Dead Stop
Gnome it Movement Captain or First Mate DC15 Deception to perform feint. Pursuing ship’s captain must succeed on DC14 Insight check to avoid getting disadvantage on all attack rolls
Surface Movement Captain or First Mate Underwater ship comes to surface. Make DC5+SZ Dexterity check. On failure the breaching is erratic and the crew cannot perform any orders next turn
Dive Movement Captain or First Mate Ship must be able to operate underwater. Ship dives underwater. Make DC5+SZ Strength check. On failure ship submerges unevenly and crew cannot perform any orders next round
Faster! Movement Captain or First Mate Increase speed by 5 feet per round. 2D10 hull damage per round for as long as this is maintained
Ramming speed! Movement Captain or First Mate Requires Oars or Paddles and a Naval Ram component upgrade, and must be within 100ft of target. Increases movement by 30 feet per round for two rounds. If it manages to get within range, it can make an attack versus the target ship’s hull. On hit target takes 20D10 damage and ram component takes 10D10 damage. Both ships reduced to 0 speed and locked together (DC18 Strength required to break free). On failure, ramming ship comes to full stop for 1D6 rounds
Launch: scout Movement Captain or First Mate Two mounts launched, who scout immediate area. They make a DC14 Perception check (using CQ modifier). On success ship gains 5 feet of speed until next tracker adjustment
Reduce speed Movement Captain or First Mate Reduced speed to a minimum of 10 feet per round. Ship may come to a stop next round
Debris Attack Bosun Standard action. Drop flaming barrels to reduce pursuing vessel speed by 5ft until distance changes. Costs 1 ship store.
A little surprise Attack Bosun Standard action. Distance 400ft or closer. Drop explosive barrel in water. Intelligence + Proficiency attack roll against pursuing ship AC. 4D10 damage in 15ft radius on success.
Improvised shot Attack Bosun DC12 CQ check to find 2 shots of improvised catapult ammunition. Does 3D10 damage with half range values of the weapon used. Can be used to fire living objects, who will take 1D6 damage per 10 feet travelled
A new paint job Buff Bosun Spend 1D10 x Ship length gold to gain +2 Ship Charisma for 1 month. Can only be used once every 3 months
Swabbing the deck Buff Bosun DC5+SZ CQ check to gain +2 Ship Charisma until end of next combat. Takes a day to complete, and cannot be done more than once between combat encounters
Wet that! Buff Bosun Gain advantage on all saving throws to resist fire damage for the next two hours
Jury rig Repair Bosun DC14 CQ check to restore 5D10 HP to a component. Consumes 1 supply store
All hands on deck Repair Bosun Standard action, can use any number of orders. Repair 2D10 Hull HP per order spent. Consumes 1 supply store per order used
Bucket chain! Repair Bosun Requires Bilge Pump upgrade. All saving throws against sinking done with advantage until next turn.
Cannibalize Repair Bosun Standard Action. Requires two turns to complete. Deal 5D10 damage to one component to heal the same amount on another component
Fix her up Repair Bosun Repair 10D10 damage on a single component. Takes 8 hours to complete, uses 1 supply store
Miracle worker Repair Bosun Use full crew for 12 hours to fully restore ship HP. Ship loses 1D6 Charisma. Consume 1 supply store for every 80HP repaired
Drydock Repair Bosun Spend 10gp per foot of ship’s length to have shipwrights in drydock repair ship. Full HP and +1 Charisma to ship after 24 hours
Target component Attack Quartermaster DC5+SZ Investigate check to target specific ship component within 300ft with advantage. Failure means attack against target hull with disadvantage
Target squadron Attack Quartermaster Attack incoming squadron or mounted unit within 200ft with harpoon or ballista. Extra 2D10 damage
Weighted shot Attack Quartermaster Attack at half range. Pass DC14 CQ check to add extra 1D10 damage
Scrounge up supplies Buff Quartermaster Pass CQ check (DMs discretion). Increase stores of food and drink by 1D3 on success. Requires suitable forage area
Hunt Buff Quartermaster Uses full crew, takes 4 hours to complete DC14 Survival check to find prey, then ballista or harpoon attack vs AC13. Success increases food store by 1D2. Takes 4 hours to complete
Rally for pay Buff Quartermaster Offer 5gp or 10gp reward to each crewmember on victory. Improves CQ by 1 or 2. If not paid after battle, suffer -3 crew quality until next payday
Rig for speed Movement Quartermaster DC5+SZ Dexterity check to increase movement speed by 5 until either end of combat or 8 hours have passed (whichever happens first)
Lighten the load Movement Quartermaster DC12 CQ check. On success reduce ship’s stores by 2 or remove 2 tons of cargo to increase speed by 5ft until next resupply
Collect flotsam or jetsam Movement Quartermaster DC12 CQ check. On success haul up 1 store worth of objects, 10 humanoid creatures, 5 large creatures or 1 huge creature. Ship speed reduced by 20 for this round
Maximum casualties Attack Surgeon Max range 100ft. Single weapon from component attacks vs target helm AC. Damage against crew, 1 casualty per 5 damage
Old sea bones Attack Surgeon Targets sea creature. DC5+CR Medicine check to make next attack have advantage and deal additional 2D10 damage
Butcher’s work Buff Surgeon Option 1: Restores any number of killed/disabled crew members. CQ check, where the DC is equal to 10 + the number of crew members you want to restore, consumes 1 medical store.

Option 2: Paladin uses standard action and 5 points of their Lay on Hands ability to restore 1D4 sailors
Invigorating tonic Buff Surgeon Use 1 medical store to add +1 to CQ
Heal up Buff Surgeon Standard action. Use 1 medical store to heal 1D8 HP to any character with 10 feet who is on the ship
Medicinal herbs Buff Surgeon Crew forages supplies to increase medical store. Requires multiple checks, refer to DM
Rest in a bottle Buff Surgeon Use 1 medical store to remove overexertion penalty or remove 1 level of exhaustion from a PC. Bad things happen if you take it multiple times
Insanity Movement Surgeon Ship speed increased by 5ft per round, and can perform 1 additional order, for 1D8 rounds. Afterwards, 1D10 sailors die. Players taking this potion gain 5ft extra speed and 1 additional bonus action. At the end they gain 2 levels of exhaustion.
Distraction Attack Ship’s Mage Standard action. Force target ship within 100ft to take DC13 CQ check or lose 1 order for that round.
Sparkling Lights Buff Ship’s Mage Reduce target mounted unit squadron within 100ft attacks by 1D10 for the round
Ward Buff Ship’s Mage DC14 Arcana check to impose disadvantage on the next spell attack made against ship
Disrupting hex Buff Ship’s Mage DC15 Arcana check to give advantage to ship and crew for saving throw against spell that has been in effect for one round or more
Protection of Magics Buff Ship’s Mage DC13 Performance check to increase CQ by 1
Wind! Movement Ship’s Mage Standard action. Increase movement by 10 for 1 round (or longer if Concentration is maintained, up to 10 rounds). Max daily use depending on level
Invisible workforce Movement Ship’s Mage Requires paddles, oars or flippers. Increasemovement by 20 feet for up to 10 rounds (requires concentration). Max daily use depending on level
Read the wind Movement Ship’s Mage Sail ships only. DC5+SZ Survival check. to increase speed by 10 feet for one round
Control currents! Movement Ship’s Mage Underwater ships only. DC5+SZ Survival check. to increase speed by 10 feet for one round
Ship mending Repair Ship’s Mage Standard action. Repair 1D10 HP to any ship components. Max 3 per long rest

Boarding combat

Once two ships have reached 0 distance on the tracker, boarding combat can begin. The ships are now very close, and the following orders become available for the most senior officer remaining:

Order Effect
Board Attackers can make DC12 CQ check to leap to other ship. PCs can use DC12 Acrobatics for the same purpose. No combat on failure
Grapple Ship Strength vs target ship’s Hull AC check. Success reduces both ship speeds to 0 and neither can pull away. Crew can move freely from ship to ship
Pull away Break grapple on successful opposed ship Strength check
Repel Boarders DC14 Persuasion or Performance check to gain +2 CQ for combat duration. Cannot be used if Have at ‘em has been issued
Have at ‘em DC14 Intimidation or Persuasion check to gain +2 CQ for combat duration. Cannot be used if Repel Boarders has been issued
Strafe the decks Attack target ship with weapons at close range. Weapon attack against target ship hull. On hit, 1D10 sailors gravely wounded. Friendly fire possible, casualties split 50/50
Protect the… Assigns crew members to protect officers, adding 10 temp HP per crew member (20 if they are Ship’s Guard)

During boarding combat, the PCs focus on enemy officers and vice versa, while the regular crews fight one another. This is done as follows:

In addition to these rules, the following modifiers may apply in crew to crew combat: