Way of Fish-Man 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, as Koala apparently is able to use it despite being human. 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.).

the secret of Fish-Man Karate is mastery of the water in the user's direct vicinity, using its power to send powerful waves impacting the water within the opponent's body. Because every creature has a high percentage of water in their body, the users of Fish-Man Karate are able to battle opponents that are usually highly resistant (if not immune) against blows and punches. This was demonstrated against Monkey D. Luffy, a rubber man, who is nearly immune to blunt attacks

Fish-Man Karate Technique

When ever you make a sucessfull unarmed strike, you can apply a Fish-man karate move.

Hyakumaigawara Seiken (literally meaning "Hundred Tile True Punch"): A hard punch that can send an opponent flying. You claims that this attack is so strong that it can break through one hundred tiles.

Wanto Giri (literally meaning "Arm Blade Slash"): You slams his arm-fin into the back of his opponent's neck.

Itomaki Kumite (literally meaning "Devilfish Sparring"): Done underwater, You wraps his ponytail(or Bite depend on fish-man animal) around the opponent's waist to prevent them for escaping. which is what his opponent looks like when they are caught by this attack. 

Uchimizu (literally meaning "Water Shot"): Jinbe hurls a simple droplet of water at his opponent, which can become a deadly bullet with the kinetic force created by his immense fish-man strength. 

Fish-Man Karate Refocus

At 6th level, you gain the ability to heal yourself. As an action, you can regain hit points equal to three times your monk level. You must finish a long or short rest before you can use this feature again.

Fish-Man Karate Hidden Technique

Beginning at 11th level, your Fish-man Karate is twice as strong in the water now,  and you can control the water, and move swifter in the water.

Samegawara Seiken (literally meaning "Shark Tile True Punch"): A powerful straight punch similar to Jinbe's usual seiken that transmits the force of the impact through the water in a person's body, enabling the strike to bypass a person's defenses; even those of devil fruit users. Just one blow was enough to overpower Gecko Moria even after Moria had absorbed several shadows into himself to increase his strength.

Nanasenmaigawara Mawashigeri (literally meaning "Seven Thousand Tile Roundhouse Kick"): Jinbe performs a roundhouse kick, which is strong enough to block the gigantic WadaTsumi's punch and break one of his fingers.

 

Vagabond Drill

At 17th level, you gain the ability to set up lethal vibrations in someone’s body. When you hit a creature with an unarmed strike, you can spend 3 ki points to start these imperceptible vibrations, which last for a number of days equal to your monk level. The vibrations are harmless unless you use your action to end them. To do so, you and the target must be on the same plane of existence. When you use this action, the creature must make a Constitution saving throw. If it fails, it is reduced to 0 hit points. If it succeeds, it takes 13d10 Force damage.

You can have only one creature under the effect of this feature at a time. You can choose to end the vibrations harmlessly without using an action.