Way of the Open Sea

Where most monks spend their lives in monasteries, one the streets, or travelling the lands, monks of the open sea gain their disciplines from being out on the ocean. They enhance their attacks with the crashing of the waves, creatures of the deep, and ferocity of the storms, becoming a force of nature themselves. 

Power of the Sea

Starting when you choose this tradition at 3rd level, you gain proficiency with sea vehicles.

Additionally at 3rd level, you gain the ability to gain the ability to harness ki and the power of the ocean. Whenever you hit a creature with an attack granted by your flurry of blows, you can impose one of the following effects on the target:

• It must succeed on a Strength saving throw or have their speed reduced to 0 until the start of your next turn as ice freezes them in place. 
• The target must succeed on a Wisdom saving throw or become frightened as visions from the deep swirl in their mind. 
• Another target within 15ft of the initial target must succeed on a Dexterity saving throw or have lighting arc towards them taking lightning damage equal to your martial arts die, taking half damage on a success.

Aquatic Adept

At 6th level you gain a swim speed equal to your movement speed and attacks made with your monk weapons or unarmed strikes are not imposed with disadvantage while underwater. Additionally, you can the ability to breath underwater.

Riptide

By 11th level you have become one with the ocean, unlocking its power. Your martial arts die becomes one dice higher than the one shown on the monk table (to a maximum of 1d12). Additionally, your unarmed strikes can deal cold or lightning damage (your choice). 

Terror from the Depths

At 17th level, you can become master of the creatures of the deep, transforming yourself into an amalgamation of them.

As a bonus action, you transform into a creature of dread. For 1 minute you can the following benefits:

• You size becomes Large
• Slimy mucus or thick scales cover your body grating you a +3 to your AC
• Four tentacles grow from your back allowing you to make an extra attack as a part of the attack action (3 total). You can advantage to grapple when attacking with these tentacles and can have multiple targets grappled at once to a maximum of 4. These tentacles use your martial arts die for damage.

You keep all featured gained from other class features while transformed. Once the transformation ends, you cannot transform until after a long rest.