The other race that dwells in the oceans, Merfolk normally possess more humanlike qualities on their top half than Fishmen though their lower half is always fish-like in nature. They are by far the fastest swimmers in the world bar none and have the unique ability to communicate with underwater creatures.
When choosing a Merfolk you must also select an Fish Bloodline to gain.
Ability Score: +2 WIS or CHA, +1 DEX or INT.
Size: Small or Medium
Speed: 20 ft land, 50 ft water
Fish Friend: You may communicate freely with any aquatic animals (Sea Kings do not count as animals). They are automatically friendly towards you and will freely give you any information they know and complete simple tasks unless there is a compelling reason they would not be. If they are not friendly you have advantage on Persuasion checks to convince them otherwise.
Water Mastery: You gain the Shape Water technique and the Cold affinity. At level 5 you can use Create and Destroy Water once per long rest at no energy cost. At level 11 you can use Control Water once per long rest at no energy cost.
Gilled: You can breathe underwater. This feature causes you to go unconscious if you would receive 10 or more ranks of exhaustion due to a Devil Fruit's Curse
Clownfish
The layer of mucous coating your skin provides you protection against toxins. You gain resistance to poison damage. At level 11 you become immune to poison damage.
Koi
You gain +5 to all movement speeds you possess. You are able to push your mobility to the absolute limits. One per long rest you are able to exert yourself, as a bonus action you may double all movement speeds you posses for three turns.
Flounder
Your flat body is able to easily blend into surroundings. While you remain motionless for over 1 minute you have advantage on stealth checks. At level 5 you may use the technique Invisibility once per long rest, at level 11 you may also use Greater Invisibility once per long rest. WIS or CHA is your Technique Ability Modifier for these Techniques.
Oarfish
Your elongated serpent like body is hard to pin down. You have advantage against grapple checks or any checks that would impose the restrained condition. At level 11 you become immune to the restrained condition.
Coelacanth
You are able to generate a small electromagnetic field used to sense other creatures. You gain Blindsense up to 20 ft around you. This range is extended to 60 ft while submerged in water. At level 11 you gain True Sight as well with the same range.
Sea Horse
You are easily able to carry others across the water. You gain +5 to all movement speeds you possess. You become a mountable creature that can carry creatures up to one size larger than you. While mounted, both you and your rider can take your turns simultaneously on either of your initiative counts.