The Thing Beneath The Waves

You have forged a pact with some inscrutable creature that dwells in the eternally lightless depths far beneath the surface of some notable far beneath the surface of some notable body of water. This creature's ambitions are often inscrutable, due to the inhospitable environs in which they dwell. Many look to see kingdoms brought low beneath the waves. or for the world to be consumed in unending floods. others have goals more nuanced and all the more dreadful. Entities of this type include Zoth-Ommog and the Abolethic Sovereignty. Some exceptionally powerful sea creatures like the kraken or leviathan may also be able to grant such power through pacts with mortals.

Breath of the deeps

Starting at 1st level, you are able to breathe water as easily as air. Additionally, you gain a swim speed egual to twice your speed.

Siren's Song

Beginning at 6th level, your patron teaches you the irresistible call of the sea. As an action you cause one creature you can see within 60 feet of you to make a Wisdom saving throw against your warlock spell DC. On a failure, the creature is charmed by you and must spend its next turn moving closer to you without regard for its safety. This effect ends after a number of rounds equal to your charisma modifier, or if the target takes damage. You must complete a long rest before using this ability again. 

Storm Shield

Starting at 10th level, you are protected by your patron's tempestuous magic. you have resistance to lightning and thunder damage. Additionally, when you are damaged by a creature within 60 feet of you, you can expend a spell slot as a reaction to deal 5d6 lightning damage to the triggering creature. You must finish a short or long rest before using this feature again.

Command The Gale

At 14th level, you are granted the power to summon storms. You can cast the spell control weather once without expending a spell slot, but you cannot change the temperature or decrease the intensity of precipitation or wind. You must complete a long rest before using this feature again.