Gendrin meditate deeply, remaining semiconscious, for 4 hours a day. (The Common word for such meditation is “trance.”) While meditating, you can dream after a fashion; such dreams are actually mental exercises that have become reflexive through years of practice. After resting in this way, you gain the same benefit that a human does from 8 hours of sleep.

with your keen eyesight you have proficiency in the Perception skill. Your keen vision doesn't change under water and you can see clearly.  

Being creatures of magic with strong ties to both Fey and Elemental magic you have advantage on saving throws against being charmed, and magic can’t put you to sleep. You can cast the misty step spell once using this trait. You regain the ability to do so when you finish a short or long rest.

These traits you have inherited from your Water Genasi parent. Maybe you are unaware of your ability or you have long used them to your advantage.

You can breathe air and water.

You have a swimming speed of 30 feet.

You have resistance to acid damage.

You know the shape water cantrip. When you reach 3rd level, you can cast the create or destroy water spell as a 2nd-level spell once with this trait, and you regain the ability to cast it this way when you finish a long rest. Constitution is your spellcasting ability for these spells.

The abilities from your Genasi parent are enhanced by your Fey ancestry, and you resave both Eladrin and Water Genasi Ability score improvements.  

Your Dexterity score increases by 2. 

Your Intelligence and Wisdom score increases by 1.

Your Constitution score increases by 2.

Depending on the world you grow up in,  Gendrin could claim adulthood the way elves do, and pick an adult name around the age of 100, or mature as humans and reach adulthood in their late teens.

Accustomed to twilit fey realms or dark oceans and the night sky, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray. 

You can speak, read, and write Common and Elvish. Elvish is fluid, with subtle intonations and intricate grammar. Elven literature is rich and varied, and their songs and poems are famous among other races. Many bards learn their language so they can add Elvish ballads to their repertoires. You also can speak, read, and write Primordial. Primordial is a guttural language, filled with harsh syllables and hard consonants.