Marina Guild

Commonly found on ships hunting sea serpents or water elementals the guild of the Marine aims to eradicate the beasts of the sea and make the ocean safe for all. They harness the powers of the ocean to hold enemies still as they chase them down and slay them. Hiding, running and fighting are not an option for the evil that lies beneath the lapsing waves of the open sea. 

Practiced Sailor

You gain Proficiency in Navigator's tools along with either Acrobatics, Nature, Perception, Sleight of hand or Survival. You may replace the ability score used for any of these skills with intelligence.

These are vital skills all sailor's need to stay afloat, spot hazards, tie knots and avoid tumbling when the serpents rise from their murky depths.

Acrobatics

You gain the skill Acrobatics 

Nature

You gain the skill Nature

Perception

You gain the skill perception

Sleight of Hand

You gain the skill sleight of hand

Survival

You gain the skill survival 

Slayer of the Sea

Upon hitting a creature with a swim speed that is in your grimoire you can mark that creature with a reaction. When you hit them you a marked creature you deal an additional 1d6 damage to them and your get a critical hit on 19s as well as 20s. You can share this knowledge with your allies any other creature within 60ft of you that can hear you also get the boosted critical chance. If you or they already have boosted critical chance such as from the champion sub class their crit chance boosts by one. 

This can be done a number of times equal to your int modifier and last 10 minutes.

Even Footing

You gain a swim speed equal to walking speed + 20ft, you may fight normally even when underwater or fighting a creature in water. Additionally you can cast the spells water walk and water breathing once per short rest. 

Menace of the Marine

You mark now deals 3d6 and the crit chance increases by one (18-20 now) there is now no limit the uses and any creatures of the same type (eg Aberration or elemental) as the one that was marked also are marked. Allies within 60ft also gain the crit chance boost. 

No Escape for the Wicked

When moving towards a creature in your grimoire your speed is doubled however you must make an attack or cast a spell against them else you will lose your bonus action. Upon hitting an enemy your weapon is considered to have slow as well as any other weapon masteries it may have.

Additional you have advantage in perception or investigation to see hidden creatures that are in your grimoire. If a DM does not want you to know their are hidden creatures there they may choose to add a +5 to your roll instead.

Any creature with a swim speed is considered to be in your grimoire.

Grasping Waves

You can cast any mixture of the spells Hold person, Hold Monster, Dominate Person, Dominate Beast and Freedom of Movement (all cast at 5th level) a number of times a day equal to your Intelligence modifier.

When these spells (except Freedom of Movement) are cast the creature they were cast on is wrapped in water giving them vulnerability to cold and lighting damage.