Mariner’s Armor 5e – Swim Speed & Life Preserver

Last Updated on January 22, 2023

Nautical campaigns, or even underwater adventures, are kind of a niche thing in Dungeons & Dragons 5e.

Officially, there’s the excellent Ghosts of Saltmarsh campaign book, which casts a wide net through a shoal of delightfully spooky aquatic adventures from the earliest days of D&D, including evocative titles like the Sinister Secrets of Saltmarsh and The Final Enemy.

Otherwise, however, there’s not a whole lot of meat on this particular fish bone. 

That’s kind of a shame, because some of the explicitly underwater-themed items found in the Dungeon Master’s Guide are among the most fun found anywhere in the game.

Chief among them is the Mariner’s Armor, a great magic item that should be compulsory for any underwater adventurer worth their salt. 

This is some of my favorite item design in the whole game because it not only provides a consistent, tangible mechanical benefit, but also a really fun, unique effect that makes the Mariner’s Armor come alive. 

During the age of sail, it was relatively uncommon for sailors to know how to swim. A powerful navy with access to magical crafting abilities might approach that same problem by crafting sets of Mariner’s Armor to give drowning sailors a second chance if they go overboard.

Sea Elf commandos, armed with knives made from megalodon teeth might wear them on nighttime raids against the dreaded Sahuagin. A wizard’s apprentice might don their battered suit of Mariner’s Armor to go searching for rare spell components amid a shark-infested reef at their master’s command. 

Because Mariner’s Armor is a type of armor design, rather than a specific set (similar to a +1 magic weapon) and can be based on the following armor types, it’s an incredibly versatile magic item that can be applied to just about any character class.  

Name	Type	AC	Strength	Stealth
Padded	Medium	11 + Dex modifier	—	Disadvantage
Leather	Medium	11 + Dex modifier	—	—
Studded Leather	Medium	12 + Dex modifier	—	—
Hide	Medium	12 + Dex modifier (max 2)	—	—
Chain Shirt	Medium	13 + Dex modifier (max 2)	—	—
Scale Mail	Medium	14 + Dex modifier (max 2)	—	Disadvantage
Breastplate	Medium	14 + Dex modifier (max 2)	—	—
Half Plate	Medium	15 + Dex modifier (max 2)	—	Disadvantage
Ring Mail	Heavy	14	—	Disadvantage
Chain Mail	Heavy	16	Strength 13	Disadvantage
Splint	Heavy	17	Strength 15	Disadvantage
Plate	Heavy	18	Strength 15	Disadvantage

If you’re a dungeon master looking to give one (or more) of your players a suit of Mariner’s Armor, there are virtually no limitations on the character classes that can make use of a set – with the exception of the monk and barbarian. 

Mechanically, having your swimming speed increased to your walking speed is a huge bonus. 

Swimming (as well as climbing and crawling) costs 1 extra foot of movement, effectively halving your speed. Being able to move your walking speed (especially if you’re playing a character that has above average movement speed, like a Tabaxi, for example) underwater is a massive advantage.

This is especially important because the dangerous things you encounter underwater, from the Reef Shark to the Water Naga, are all going to be able to move at close to twice your swimming speed. 

Given the fact that characters can hold their breath for a length of time equal to 1 + their Constitution modifier (30 seconds is the minimum), being able to move further and accomplish more while submerged can be the difference between survival and a watery grave. 

The survival component of the Mariner’s Armor – which will send you rocketing towards the surface if you drop to 0 hit points – can be a literal lifesaver if you begin to drown beneath the surface.  

Where can I get Mariner’s Armor?

The cost of buying a suit of Mariner’s Armor obviously varies depending on the price of the armor type on which it’s based. Padded Armor costs as little as 5 gold pieces, and a full suit of Plate will run you an eye-watering 1,500 gp before you’ve even imbued it with any magical effects. 

In our Magic Items Pricing Guide, we can see that the cost of a common magic item can range from 50-100 gp, and that a rare magic item can be worth as much as 5,000 gp.

Mariner’s Armor is uncommon, and so sits somewhere between the two. I think that, in a “standard” magic item shop, a fairly straightforward way of pricing Mariner’s Armor (per the pricing rules for magic items in the Dungeon Master’s Guide) is to take the base cost of the armor and add 500 gp. 

However, this is a game about simulating real life, so taking the concept of supply and demand into account is also important.

A suit of Mariner’s Plate in a magic item shop located in the capital of a great empire, where there’s a wizard’s college, dwarven forges, and enchanted gear is more common, might therefore fetch the 2,000 gp that our little base cost + 500 gp rule suggests.

In a frontier town beside the ocean, where an evil Sahuagin priest is causing sea levels to rise and storms to better the coast, you could expect to shell out that same 2,000 gp for Mariner’s Padded Armor.

Conversely, a society of aquatic elves might just leave their suits of Mariner’s Scale Mail lying around, and happily outfit some helpful, polite adventurers with their own sets for free. 

In terms of places you might find a suit of Mariner’s Armor, any seafaring race of sentient creatures might have one lying around. There might be a suit of Mariner’s Leather Armor on a pirate ship, donned by whichever crew member whose job it is to swim under the enemy vessel and disable the rudder.

An order of paladins sworn to guard the shores against an encroaching race of monstrous kaiju (definitely aboleths and their giant squid servants) might have a set of Mariner’s Plate going spare from the last time they lost a brother on an away mission.

The local pearl divers might all wear Mariner’s Studded Leather for an extra dash of speed – not to mention the peace of mind that, if things go south beneath the waves. 

Conclusion 

If you’re a dungeon master looking to run a seafaring campaign, putting a suit or two of Mariner’s Armor in your game can be a great way to give your players a decidedly on-theme advantage when they venture beneath the surface of the deep blue sea.