How do hit points for massive objects, like ships, work?

Question

Page 119 of the DMG has stats for airborne and waterborne vehicles. They usually have multiple hundreds of hit points.

However, isn’t a boat a massive object? If it were, it would be subject to the rules concerning objects on pages 246-247. The rules for Huge and Gargantuan objects state that:

[...] That said, one torch can burn a Huge tapestry, and an earthquake spell can reduce a colossus to rubble. You can track a Huge or Gargantuan object's hit points if you like, or you can simply decide how long the object can withstand whatever weapon or force is acting against it. If you track hit points for the object, divide it into Large or smaller sections, and track each section's hit points separately. Destroying one of those sections could ruin the entire object. For example, a Gargantuan statue of a human might topple over when one of its Large legs is reduced to 0 hit points.

So would a ship not work similarly?

1. Does a ship sink only when it reaches 0 HP?
   The counterargument is the one about smaller sections of a massive object; if a giant hole is made in the hull of a ship, one that’s too big to patch up, then surely it will sink.

2. If a ship has HP and AC, does it count as a creature for the use of spells?
   Plenty of spells in D&D 5e don’t damage objects: fireballs and lightning bolts only light objects on fire, so would a ship count as a creature?

3. Can you target a specific sub-section of a ship? And how would damage thresholds interact with that?
   This is linked to question 1. Could a mage casting a powerful spell, or someone wielding a siege weapon, etc., actually aim for a sensitive point on a ship, and destroy that one sub-section?
   Furthermore, does a subsection maintain the damage threshold of the full structure? Warships, for example, have of DT of 20, and the stats for resilient objects show that most large objects have less than 30 HP. Does this mean that either, you do nothing to the object, or you nearly destroy it?

My reason for asking this is that spells like meteor swarm, on average, do around 160 damage (I believe it also applies to objects). This isn’t enough to destroy most ships (fair enough, the blast is too small), but surely it could destroy enough of the hull to sink most vessels, no?

Answer 1

Ghosts of Saltmarsh provides clearer rules for damaging ships.

The core rulebooks are a little ambiguous regarding ship damage: Dungeon Master's Guide p. 247 states that a vehicle is not one object, but "composed of many other objects"; while p. 119, "Airborne and Waterborne Vehicles", shows statistics as if a ship was a single object with a single hit point value.

The adventure module Ghosts of Saltmarsh, "Appendix A: Of Ships and the Sea", expands upon the rules and makes them clearer. In summary:

• A ship is divided into sections: Hull (the main ship body), Control (the helm), Movement (sails or oars), and Weapon (any ballistas, rams, cannons or the like). Each is its own independent object, with its own hit point value, armor class and damage threshold.
• The only way to sink the ship is to reduce its Hull to zero hit points. You cannot focus-fire on one section of the hull to sink the ship faster. Damaging other components like the sails or oars can hinder the ship, but doesn't help to sink it.
• The value given in the Dungeon Master's Guide for a ship's hit points, AC and damage threshold refers to the Hull. This is clear if you compare the ship statistics in the DMG to their statblocks in Saltmarsh.

To answer your questions directly:

1. Does a ship sink only when it reaches 0 HP?

   Yes.

2. If a ship has HP and AC, does it count as a creature for the use of spells?

   No, a ship is not a creature. As per both Ghosts of Saltmarsh and DMG p. 247, it is a collection of objects. This technically means fireball, which only specifically damages creatures, does not directly deal that damage to objects - although I imagine most DMs would overrule that in the pursuit of logic, as the Objects rules in the DMG state that DMs should use common sense when adjudicating attempts to damage large objects, and gives the specific example of using fire to burn a massive tapestry with ease. Fireball also ignites flammable objects, which would naturally deal damage to a wooden ship.

3. Can you target a specific sub-section of a ship?

   You can target the rigging, oars, helm, mounted weapons and so forth, but you cannot make a called shot on a specific section of the hull in order to sink it faster, just as you can't make a called shot on a dragon's head to kill it more quickly.