Heroes of Freeport
Shipboard combat is just like any other combat between the PCs and their opponents, except the encounter takes place on board a ship, rather than in a dungeon or on a forest path. For the most part, shipboard combat can be resolved normally. The only constraints are the size of the ship (and therefore, the size of the battlefield), the danger of falling overboard into the water, and the effects of weather on the ship.
If the combat happens during a storm or in rough seas, treat the ship’s deck as difficult terrain. There are plenty of things to climb, and the decks and rigging present many opportunities for vertical encounters aboard ship. In all other ways, shipboard combat functions no differently than combat on land.
Magic against Ships
The effects of most spells on ships can be determined normally. However, certain spells have different effects in naval combat. The effects of most of these spells are detailed below. The DM can use these examples as guidelines for determining how other spells not listed here affect ships.
Animate Objects: Only the smallest of rafts are rated below Gargantuan Size and thus affected by this spell.
Black Tentacles: This spell can be cast on the surface of the water, the ocean floor, or on a ship’s deck. The tentacles do not attack ships.
Blade Barrier, Cloudkill, Fog Cloud, Pyrotechnics, Stinking Cloud, Storm of Vengeance: The effects created by these spells do not move with a ship.
Call Lightning, Chain Lightning, Lightning Bolt, Scorching Ray, Storm of Vengeance: These spells do not start fires on a ship.
Control Water: The “redirect flow” option allows you to halve or double the speed of a ship within the affected area, as though the current were against or with the ship. The area of water affected by this spell does not move with a ship.
Control Winds: This allows you to halve or double the speed of a wind-driven ship within the affected area, as though the winds were against or with the ship. The area of winds created by this spell does not move with a ship.
Delayed Blast Fireball, Fireball, Fire Storm, Flame Arrows, Flame Blade, Flaming Sphere, Meteor Swarm, Produce Flame: These spells can start fires on a ship.
Dimension Door, Teleport, Teleportation Circle: Because ships are usually in motion, the caster of spells of the teleportation subschool must have line of sight to teleport onto a ship. Otherwise, a caster must scry upon a particular ship first, then immediately teleport to the scryed destination. Any delay in casting likely means the ship has moved from its scryed location and the spell fails.
Disintegrate: This spell ignores a ship’s Damage Threshold. The loss of particular portions of a ship, like the rudder or navigation wheel, may have significant effects on a ship’s ability to operate. Because this spell affects only discrete objects, using it on a ship’s hull only destroys a single plank; this creates no more of a worry than being holed by a cannon shot and is no more difficult to repair than indicated by the spell’s normal damage roll.
Fabricate: The ability to manufacture processed items allows ships repairs to occur quickly; each casting of this spell represents one day of labor for a semi-skilled craftsman. Very few portions of a ship require a high degree of craftsmanship to process.
Flame Strike: The divine nature of this fire is such that it will not start fires on a ship unless applied to exposed oil or gunpowder.
Forcecage, Resilient Sphere, Wall of Force: The effects of these spells move with a ship if they are anchored to it. Otherwise, they do not move with a ship, and a ship running into them makes a ramming maneuver.
Freezing Sphere: This spell can be used to trap a ship in ice by targeting the water around the ship. The ship’s speed is reduced to 0 for the duration of the spell.
Gaseous Form: A creature in gaseous form does not move with a ship unless within an enclosed area (a cabin or below decks).
Globe of Invulnerability, Tiny Hut, Wall of Ice, Wall of Thorns: The effects created by these spells move with a ship.
Guards and Wards, Mordenkainen’s Private Sanctum: These spells can be cast on a ship.
Ice Storm, Sleet Storm: The sleet, snow, and ice created by these spells do not move with a ship, but the deck is considered icy. At the DM’s discretion, these spells will extinguish existing fires.
Incendiary Cloud: The cloud created by this spell does not move with a ship, but the caster can concentrate to move the cloud along with a ship. This spell can start fires on a ship.
Magic Weapon: These spells also affect siege engines and siege engine ammunition.
Mirage Arcana: Ships are considered structures for the purposes of this spell.
Mordenkainen’s Magnificent Mansion, Rope Trick: The entrances to the extradimensional spaces created by these spells do not move with a ship.
Passwall: Using this spell on a hull, below the waterline, is a sure way to sink a ship. A hole with an area of 40 square feet causes even a large ship to become submerged within 1d10 minutes. Note that some ship hulls are lined with copper or other materials not affected by this spell.
Prismatic Spray, Prismatic Wall: The (red) fire effects can start fires on a ship. A prismatic wall moves with a ship only if it is anchored to the ship.
Reverse Gravity: A ship must fit entirely within the spell’s area for the ship itself to be affected by this spell, though creatures and objects on a ship’s deck are affected normally. If an entire ship is affected, its falling damage upon returning to the water is not reduced by its Damage Threshold.
True Polymorph: A ship is a collection of numerous objects. As a result, any ship of Gargantuan size (which includes all but the smallest rowboats or rafts) is too big to be affected by this spell.
Wall of Fire: A wall of fire cast on the deck of a ship moves with the ship and can start on-board fires. Otherwise, the wall does not move with the ship, and does not start on-board fires.
Wind Wall: The effects of this spell move with a ship if it is anchored to the ship. A small sailing ship (a keelboat or a masted rowboat or raft) can use this spell to great advantage; treat such a vessel as having the wind in its favor for the spell’s duration if the wall is correctly positioned behind the sail.
Unless aided by magic, a character can’t swim for a full 8 hours a day; after each hour of swimming, a character must succeed in a DC 10 Constitution saving throw or gain one level of exhaustion.
A creature that has a swimming speed—including a character with a ring of swimming or similar magic—can swim all day without penalty and uses the normal forced march rules in the Player’s Handbook.
Swimming through deep water is similar to traveling at high altitudes, because of the water’s pressure and cold temperature. For a creature without a swimming speed, each hour spent swimming at a depth greater than 100 feet counts as 2 hours for the purpose of determining exhaustion. Swimming for an hour at a depth greater than 200 feet counts as 4 hours.
Visibility under water depends on water clarity and the available light. Unless the characters have light sources, use the Underwater Encounter Distance table to determine the distance at which characters under water become aware of a possible encounter.
Underwater Encounter Distance
|Creature Size||Encounter Distance|
|Clear water, bright light||60 ft.|
|Clear water, dim light||30 ft.|
|Murky water or no light||10 ft.|