Sea Horse 5e: The Underwater Familiar

A sea horse is a CR 0 Tiny Beast worth 0 XP, with AC 11, 1 hit point, a 20-foot swim speed and no attacks at all. It can breathe only underwater. Nobody fights a sea horse. People search for it because it's a Find Familiar option in both editions, and one of the few that can scout underwater. The 2024 Seahorse adds Stealth +5, a 5-foot walk speed and Bubble Dash, an action that lets it swim its full 20 feet without provoking opportunity attacks.

Table of Contents

• •Sea Horse Stat Block (2014)
• •The Seahorse (2024)
• •The Sea Horse as a Familiar
• •Out of the Water
• •How Sea Horses Fight (They Don't)
• •Sea Horses in Encounters
• •How Players Beat the Sea Horse Polymorph
• •Frequently Asked Questions

Sea Horse Stat Block (2014)

The Seahorse (2024)

Both have 1 hit point and Water Breathing, and both are CR 0 for 0 XP.

The Sea Horse as a Familiar

2014. Find Familiar lists "sea horse" by name. The familiar has the sea horse's statistics but is a celestial, fey or fiend, and it can't attack (the sea horse has no attack anyway). While it's within 100 feet you can talk to it telepathically, and as an action you can see and hear through it.

2024. Find Familiar no longer names the sea horse, but it allows "another Beast that has a Challenge Rating of 0", and the Seahorse qualifies. Seeing through its senses is now a Bonus Action. The 2024 form is the better scout: Stealth +5 to stay unseen, and Bubble Dash to swim away from anything that notices it.

What it's good for: scouting a flooded dungeon, checking under a ship's hull, delivering a touch spell underwater (a familiar in either edition can deliver one with its Reaction), or finding the way through a sunken passage before the party commits its Water Breathing.

Out of the Water

The SRD doesn't say how long a water-breather survives in air, so this applies the Suffocation rule as written. That's a DM ruling, not rules text.

• •Holding its breath. Con 8 gives a −1 modifier, so 1 + (−1) is 0 minutes. Both editions set a minimum of 30 seconds: 5 rounds.
• •2014 after that: it survives rounds equal to its Con modifier, minimum 1, then drops to 0 hit points.
• •2024 after that: it gains 1 Exhaustion level at the end of each of its turns, and dies at level 6.

For a familiar, the fix is easy. Dismiss it to its pocket dimension while on land and call it back (within 30 feet) once you reach water.

Polymorph. CR 0 means a sea horse is a legal Polymorph form for any creature. In 2014, a polymorphed creature on land drops to 0 hit points after its breath runs out and reverts to its normal form. In the 2024 rules the target keeps its own hit points and gains 1 temporary hit point, and the spell ends when that runs out. Any hit, for example from one of the target's allies, ends the spell. Applied literally, the 2024 Suffocation rule would let Exhaustion build to the lethal level 6 before the hour-long spell ends. That's a strong outcome for a 4th-level spell. Decide how you'll rule it before a player tries it.

How Sea Horses Fight (They Don't)

A sea horse has no attack. In 2014 it has no action at all; in 2024 its only action is Bubble Dash, which is a retreat. When threatened it swims away. A 2024 seahorse can take the Hide action instead of Bubble Dash: Stealth +5 against DC 15 succeeds on a 10 (55%).

Sea Horses in Encounters

A sea horse is worth 0 XP, so it's scenery and signal. A school of sea horses scattering is a sign something bigger is coming. Their larger kin, the giant sea horse, is an aquatic mount; the SRD 5.1 says aquatic elves train them.

For players, a sea horse is also a Wild Shape form: from druid level 4 in 2014 (it has a swim speed) or level 2 in 2024. It's a water-breathing scout form with 1 hit point. In 2024 the druid keeps their own hit points and gains temporary hit points equal to their druid level, so the form is far less fragile there.

How Players Beat the Sea Horse Polymorph

If an enemy caster turns a party member into a sea horse on dry land:

• •Hit your friend. One point of damage ends it. In 2014 the sea horse drops to 0 hit points and the target reverts with no excess damage. In 2024 the single temporary hit point is gone and the spell ends.
• •Get it into water. A bucket, a barrel or a pond lets it breathe and stops the clock.
• •Break concentration on the caster, or end the spell with Dispel Magic.

Frequently Asked Questions

Can a sea horse be a familiar in 5e?

Yes, in both editions. The 2014 Find Familiar lists sea horse by name. The 2024 spell allows any Beast with Challenge Rating 0, which includes the Seahorse.

What CR is a sea horse?

CR 0, worth 0 XP. It has AC 11 (12 in 2024), 1 hit point and no attacks.

Can a sea horse breathe air?

No. Its Water Breathing trait says it can breathe only underwater. Out of water, applying the Suffocation rule (a DM ruling; the SRD doesn't cover it), it holds its breath for 30 seconds. After that a 2014 sea horse drops to 0 hit points a round later, and a 2024 Seahorse gains 1 Exhaustion level at the end of each of its turns.

What does Bubble Dash do?

It's the 2024 Seahorse's only action: while underwater, the seahorse moves up to its swim speed (20 feet) without provoking opportunity attacks.

Stat blocks: System Reference Document 5.1 (2014) and 5.2.1 (2024), Wizards of the Coast, CC-BY-4.0. Tactics, encounter math and ideas are Loreify's own.