Fishman Karate

Fish-Man Karate is a martial art that is practiced by certain skilled members of the fish man race; it is noted that humans can also learn the fighting style, While deadly enough on land, Fish-Man Karate has a number of devastating underwater moves designed to be suitable with the Fish-Man strength and speed along with the mobility that goes while under water and, in some cases, a fish-man's personal adaptation (fins, teeth, etc.).

Hundred tile fist

Hundred tile fist:  you can spend 1 Ki point to use  Hundred tile fist after a successful flurry of blows. Hundred tile fist is a hard punch that will send your opponent flying dealing 1d6 damage (2d6 if underwater) if your opponent doesn't succeed in a dex saving throw of 10 they are knocked prone.

Shark Grip

Shark grip gives you advantage on grappling. by using 1 Ki point it allows you to when an opponent is grappled squeeze them and deal 2d4 damage.

Sharkskin palm block

sharkskin palm block allows the user to as a reaction the user can have the opponent roll a dex saving throw if it is 10 or higher the attacks damage is halved if they fail they saving throw the attack is negated and if the opponent was using a weapon that weapon is knocked out of the users hand costs 2 Ki points

Arabesque Tile True Punch

By spending 2 Ki points you can use Arabesque Tile True Punch. Arabesque Tile True Punch allows the user to punch in the direction of an enemy  which then transfers the blow through the water vapor in the air to hit the target with a shock wave that hits anyone in the general area dealing 3d10 damage and knocking the opponent directly hit with it prone and everyone around the target rolls a dex saving throw if they get a 10 or higher they will succeed if they fail they are knocked prone as well.

Arrow Military Shark

if the user wets there arm along with spend 1 ki point they can hurl the water droplets at an opponent to deal 2d6 damage for each hit. can be used up to 6 times.

7000 Brick Roundhouse Kick.

use 2 Ki points to deal massive damage to an a=enemy close by. dealing 3d12 damage.

Haki

Starting off you can only use haki for 20 minutes ( attacks) but every level you gain another 5 minutes. 12th(5 attacks), 13th(6 attacks), 14th(7 attacks), 15th(8 attacks), 16th( 9 attacks), 17th(10 attacks), 18th(11 attacks), 19th(12 attacks), at 20th level you can use it for 20 attacks. haki allows you to do double damage with you attacks.

body water displasement

by spending 2 Ki points you can hit somone and ignore their AC as you displace the water in their body. every attack is guaranteed but half damage

water shark bomb

you can start charging a water bomb above your head by spending 5 Ki points and every turn spent charging it is an extra 2d6 for damage (maxes out at 10).