Giant Sea Horse 5e: The Underwater Mount That Rams

A giant sea horse is a CR 1/2 Large Beast with AC 13, 16 hit points and a 40-foot swim speed. It can breathe only underwater. In the 2014 rules its Ram is weak (+3, 4 damage) until it charges: after 20 feet of straight movement, a hit adds 7 (2d6) and forces a DC 11 Strength save against being knocked Prone. The 2024 Giant Seahorse hits harder every time (9, or 11 after a charge), loses the knockdown, and gains Bubble Dash, a bonus action that swims it 20 feet away without provoking opportunity attacks. It's the SRD's example of an aquatic mount.

Table of Contents

• •Giant Sea Horse Stat Block (2014)
• •The Giant Seahorse (2024)
• •How Giant Sea Horses Fight
• •How Players Beat Giant Sea Horses
• •Riding a Giant Sea Horse
• •Giant Sea Horse Encounter Ideas
• •Frequently Asked Questions

Giant Sea Horse Stat Block (2014)

The SRD 5.1 text calls giant sea horses shy, colorful fish and says aquatic elves train them as mounts.

The Giant Seahorse (2024)

How Giant Sea Horses Fight

2014: one big hit. Against AC 16 the +3 Ram hits on a 13 (40%). A charge hit deals 11 on average. Without the run-up it's 4. Play it as a skittish animal: charge once, then flee and circle.

2024: the charge loop. Bubble Dash makes the 2024 seahorse a hit-and-run attacker. Each turn it swims 20+ feet straight at a target, rams for 11, and uses Bubble Dash to swim 20 feet back out without an opportunity attack. Next turn it's 25 feet away, exactly enough room for a 20-foot charge. At +4 against AC 16 that's 45% for 11, about 5 damage a round, and melee characters never get an opportunity attack against it.

Out of water. Water Breathing means it can't breathe air. On land it has a 5-foot walk (2024) or no walk speed at all (2014). The SRD doesn't say how a water-breather fares in air, so applying the Suffocation rule is a DM ruling. Under the 2024 rule it holds its breath for 1 minute (1 + its Con modifier of +0), then gains 1 Exhaustion level at the end of each of its turns, and loses those levels once it's back in water. Under the 2014 rule it lasts 1 minute plus 1 round, then drops to 0 hit points.

Encounter math. Two giant sea horses against four level 2 characters is Low under the 2024 budget and Easy under the 2014 guidelines. Add two merfolk riders and it becomes Medium by the 2014 numbers in our encounter calculator (still Low in 2024).

How Players Beat Giant Sea Horses

• •Ready an attack. Characters without a swim speed swim at half speed (15 feet for most), so they can't close the 25-foot gap the 2024 seahorse leaves each turn and still attack. A readied attack that triggers when it comes within reach is the practical way to hit it in melee.
• •Use piercing weapons. Underwater, characters without a swim speed have Disadvantage on most melee weapon attacks. The 2014 exceptions are the dagger, javelin, shortsword, spear and trident; in 2024 any piercing weapon is exempt.
• •Calm it. With Int 2, Animal Friendship works in both editions, and a shy animal that stops attacking is the best outcome if you want to ride it later.

Riding a Giant Sea Horse

• •You can't buy one. The SRD 5.1 equipment chapter says aquatic mounts such as giant sea horses are rare and not normally for sale. Getting one means raising it from an egg, making a bargain with a powerful entity, or negotiating with the mount itself.
• •You need an exotic saddle. Both SRDs say an exotic saddle (60 gp) is required to ride an aquatic or flying mount.
• •You still need to breathe. The mount breathes water; you don't. Water Breathing (a 3rd-level spell) covers up to ten creatures for 24 hours.
• •Bring the right weapon. The underwater weapon rule above applies to the rider, so pack a spear or trident.
• •Controlled mounts don't ram. A controlled mount can only Dash, Disengage or Dodge. Let the sea horse act independently if you want the charge.

Giant Sea Horse Encounter Ideas

The stable reef. A colony of sea elves (a reskin) keeps giant sea horses in a kelp corral. One has been stolen by sahuagin, and the elves will lend mounts to anyone who gets it back.

The beached herd. A storm has stranded three giant sea horses in a tidal pool that's draining. The party has about a minute per animal to get them back into deep water.

Frequently Asked Questions

What CR is a giant sea horse in 5e?

CR 1/2 (100 XP) in both editions. The 2024 version is called the Giant Seahorse and has AC 14 instead of 13.

Can you ride a giant sea horse?

Yes, with an exotic saddle, and only underwater. The SRD 5.1 names giant sea horses as an example of aquatic mounts, which are rare and not normally for sale. A Medium rider fits on this Large creature.

What is the 2024 Giant Seahorse's Bubble Dash?

A bonus action: while underwater, the seahorse moves up to half 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.