Creatures can attack ships with spells. Ships are objects, so spells that can only target creatures have no effect on ships. However, because a ship is actively crewed and piloted, it can make saving throws against spell effects. Ships are immune to most spells that require a Will save. A ship without a crew is considered an unattended object and cannot make saving throws.
The effects of most spells on ships can be determined normally. However, certain spells have different effects in naval combat. The effects of these spells are detailed on the following page. GMs can use these examples as guidelines for determining how other spells not listed here affect ships. For the most part, these effects only apply during ship-to-ship combat, not during normal combat aboard a ship, though some affects (such as starting fires), could still apply, at the GM's discretion.
Animate Objects: A ship under the control of a pilot cannot be animated with this spell without the pilot's consent. An animated ship moves as the caster directs. It needs no crew other than the caster, who is considered the ship's pilot. An animated ship's statistics, such as its hit points, do not change.
Black Tentacles: This spell can be cast on the surface of the water or on a ship's deck. The tentacles do not attack ships.
Control Water: A ship cannot leave the area affected by this spell and must take the “uncontrolled” action for the duration of the spell.
Control Winds: The area of winds created by this spell does not move with a ship.
Dimension Door, Greater Teleport, Teleport, Teleportation Circle: Because ships are constantly 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 means the ship has moved from its scryed location and the spell fails.
Earthquake: This spell has no effect in the deep waters of the ocean.
Fabricate: The materials created by this spell can be used to repair a ship.
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 attempt to trap a ship in ice by targeting the water around the ship rather than the ship itself. The ship's speed is reduced to 0 for the duration of the spell unless the pilot of the ship makes a DC 25 sailing check to break free of the ice.
Mirage Arcana: Ships are considered structures for the purposes of this spell.
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. These spells also allow a ship to make an additional saving throw to extinguish 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.
Passwall: A ship can make a Fortitude save to negate the effects of this spell. A ship affected by this spell gains the broken condition and the sinking condition, but the ship is restored to its normal condition when the spell ends (though a sunken ship remains sunk).
Polymorph Any Object: A ship is a collection of numerous objects. As a result, any ship of Huge size or larger is too big to be affected by this spell.
Prismatic Sphere, Prismatic Spray, Prismatic Wall: These spells do not start fires on a ship unless the ship passes through the spell effect and rolls a natural 1 on its saving throw against fire damage. A prismatic sphere or prismatic wall moves with a ship if it is anchored to the ship. Otherwise, it does not move with a ship.
Repel Wood: If you are standing on a ship, that ship is considered a fixed object in relation to you and is not affected by this spell. Loose objects on your ship, or on other ships within range, are affected normally. A ship under the control of a pilot can make a Will save to negate the effects of this spell.
Reverse Gravity: A ship must fit entirely within the spell's area to be affected by this spell, though creatures and objects on a ship's deck are affected normally. If an entire ship is affected and falls back down more than 50 feet, the pilot must succeed at a DC 20 sailing check when the ship lands or it gains the sinking condition.
Sympathetic Vibration: A ship is considered a freestanding structure for the purposes of this spell.
Whirlwind: Most ships are too large to be affected by this spell, but loose objects and creatures on the ship's deck may still be affected.
Wind Wall: The effects of this spell move with a ship if it is anchored to the ship.