The way of the shark is an incredibly strict monastic tradition, only those with the strongest of wills can survive their training. Yet those who do survive are incredible martial artists with near unparalleled skill in battle. They train on pain resistance on sharpened coral and build up resistance to natural poisons found on the coast. Endurance training consists of fighting the riptide. Their methods in combat are brutal and efficient as the grandmasters strongly believe and enforce the idea that fighting may be a last resort but when you must exhaust your last resort you are obligated to be merciless. (feel free to critique I haven't homebrewed before so I'd like to get better)

One with the current

At 3rd level, you have learned how to use your Ki to affect the water around you. You gain the following:

You can breathe underwater and gain a swim speed equal to your regular speed, and your monk weapon attacks underwater are no longer at disadvantage.
Cast the Shape Water cantrip as a bonus action and can cast Absorb Elements at the cost of 1 Ki, but only against Cold Damage.
When you make an Unarmed Strike you can decide to draw water from a nearby source (including the air if possible) to make a ranged attack. These attacks have a range of 30 feet, are magical, and deal slashing or bludgeoning damage equal to your Martial Arts Damage + your Wisdom modifier. When you use the Attack action on your turn to use this special attack, you can spend 1 ki point to make two additional attacks with it as a bonus action like you would for Flurry of Blows. (I used the way of the Elementalist for a template to work with if its too similar let me know)

spellcasting

Through tough and rigorous training you can now manipulate the ki within your body to cast certain spells

Blood sense

If you are tracking a wounded creature you have an advantage to your roll and if the tracking roll is successful you can identify the species of what you're tracking. Also if anything enters within a 30ft sphere of you they must make a stealth check at disadvantage or be detected.

Feeding Frenzy

When you drop an opponents health to 1/2 you receive a buff to your strength, dexterity, and wisdom. (once per long rest) up to a maximum of 30. Scaling as you level

Serrated blows

As a bonus action, you can spend 2 ki points to add your wisdom modifier of d4 to an unarmed strike

Death from below

Should your ally be struck by a melee blow when you too are in melee distance with the opponent you may use a reaction to attack the creature you receive an action/bonus action to attack and you also receive an additional unarmed strike to your flurry of blows during your reaction. Just as well upon hitting the opponent you can grapple them at the end of your reaction.