Oath of the Open Sea.

The Oath of the Open Sea calls to seafaring warriors, swashbuckling sailors, and traveling guardians who seek the thrill of a limitless horizon. Driven to search for adventure and mystery across and beneath every endless oceanic expanse, paladins who swear this oath stand against those who would deny liberty to like-minded travellers, rooting out tyranny and corruption wherever it is found.

Level 1 Features:

Tenants of the Open Sea.

Freedom can be a selfless virtue or a selfish want. For paladins who swear the Oath of the Open Sea, freedom is the highest calling, and a gift to be granted to all.
No Greater Life than a Life Lived Free. One should be free to chart their own path without oppression. Those who would exert their power to dominate others shall be smote.
Trust the Skies. The guidance of a strong breeze. The rumbling warnings of a coming storm. Nature is a source of portent and council that should be heeded.
Adapt Like the Water. The waters of the ocean can shift around any obstacle—or become the most impassable obstacle of all. They carve away the land to reveal the secrets of the past, or swallow the truth and hide it forever. To embrace this fluidity is to be ready for any challenge.
Explore the Uncharted. The world is filled with mystery. Through the pursuit of enigmatic ends, one can uncover those who hide their foul deeds, and find the path to becoming something great.

Level 3 Feature:

Oath Spells.

Each oath has a list of associated spells. You gain access to these spells at the levels specified in the oath description. Once you gain access to an oath spell, you always have it prepared. Oath spells don't count against the number of spells you can prepare each day.
If you gain an oath spell that doesn't appear on the paladin spell list, the spell is nonetheless a paladin spell for you.

Channel Divinity: Marine Layer.

As an action, you channel the sea to create a thick cloud of fog that surrounds you for 20 feet in all directions. The fog moves with you, remaining centered on you and making its area heavily obscured. You and each creature within 5 feet of you instead treat the area as lightly obscured. This fog lasts for 10 minutes, spreads around corners, and cannot be dispersed unless you choose to end this effect (no action required).

Channel Divinity: Fury of the Tides.

As a bonus action, you channel the powerful might of the waves to bolster your attacks for 1 minute. Once per turn for the duration, when you hit a creature with a weapon attack, you can choose to push the target 10 feet away from you. If pushed into an obstacle or another creature, the target takes bludgeoning damage equal to your Charisma modifier.

Level 7 Feature:

Aura of Liberation.

Starting at 7th level, you fill nearby creatures with the energy of movement. While you're not incapacitated, you and creatures of your choice within 10 feet of you cannot be grappled or restrained, and ignore penalties on movement and attacks while underwater. Creatures that are already grappled or restrained when they enter the aura can spend 5 feet of movement to automatically escape unless they are bound by magic restraints.
At 18th level, the range of this aura increases to 30 feet.

Level 15 Feature:

Stormy Waters.

At 15th level, you can call on the force of crashing waters as a reaction whenever a creature moves into or out of your reach. The creature takes 1d12 bludgeoning damage and must succeed on a Strength saving throw against your spell save DC or be knocked prone.

Level 20 Feature:

Mythic Swashbuckler.

At 20th level, you learn to channel the spirits of historic sea captains to briefly become a paragon of heroic adventure. As an action, you embrace these spirits of the sea to gain the following benefits for 1 minute:
-You have advantage on Strength (Athletics) checks and you gain a climbing speed equal to your walking speed. If you already have a climbing speed, it is doubled.
-If you are within 5 feet of a creature and no other creatures are within 5 feet of you, you have advantage on attack rolls against that creature.
-You can take the Dash or Disengage action as a bonus action.
-You have advantage on Dexterity checks and Dexterity saving throws against effects you can see.
Once you use this feature, you can't use it again until you finish a long rest.