Merfolk

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 +10 to all movement speeds you possess. You are able to push your mobility to the absolute limits. A number of times equal half your proficiency bonus per long rest rounded down, you are able to exert yourself, as a free 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 Blindsight 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.

Anglerfish

The bioluminescent lure on your head can distract and disorient enemies. You can cast the Light technique at will. Starting at level 5, you can cast the Hypnotic Pattern technique once per long rest. WIS or CHA is your Technique Ability Modifier for these Techniques.

Dolphin

Known for your intelligence and agility, you excel in both combat and problem-solving. You gain proficiency in the Acrobatics and Insight skills. At level 11, you can use the Evasion feature, allowing you to take no damage on a successful DEX saving throw and half damage on a failed one.

Octopus

Your flexible body and ink defense make you hard to catch. You gain the ability to use Ink Cloud once per long rest, creating a 20-foot-radius sphere of ink in water that heavily obscures the area for 1 minute. Starting at level 5, you can use the Tentacle Slam technique once per long rest, making a melee attack against all creatures within a 10-foot radius. WIS or CHA is your Technique Ability Modifier for these Techniques.

Stingray

Your barbed tail can deliver a venomous sting. You gain a tail attack that deals 1d4 + DEX modifier piercing damage and imposes the poisoned condition on a failed DC (8 + Proficiency + CON mod) Constitution saving throw. At level 11, the damage increases to 1d8, and the poisoned condition lasts for 1 minute.

Jellyfish

Your translucent body can emit a paralyzing shock. You gain resistance to lightning damage. At level 11, you can use the Paralyzing Shock ability once per long rest, forcing a creature within 5 feet to make a DC (8 + Proficiency + CON mod) Constitution saving throw or be paralyzed for 1 minute. They can repeat the save at the end of each of their turns to end the effect.

Sea Turtle

Your sturdy shell provides exceptional defense. You gain a +1 bonus to AC. Starting at level 5, you can withdraw into your shell as a bonus action, gaining resistance to all damage except psychic until the start of your next turn. At level 11, this resistance extends to your allies within 10 feet.