You have 80 ft swimming speed, and 30 ft hovering speed.

Much like water, you are constantly changing. Because of this constant change, every time you gain a level, you can change where your racial ability score is applied. (+2 to a score of choice and +1 to a score of choice) One must be physical (Con, Str, Dex), the other must be mental (Cha, Wis, Int).

You heal 4 hit points from water spells or water attacks that deal a maximum damage of 10 or more. You are immune to all water attacks and spells.

Light Rain will heal you fully when you are not in combat. Medium Rain make you larger, causing enemies to have to roll for an intimidation check if it rains during a battle. If the check is passed, the target will continue the fight as normal. If the check is failed, the fear spell will be cast to the target. Heavy Rain is fast and goes right through you like a bullet, it will take some of the water you are made of with it. You take 1d4 piercing damage for every hour you are in Heavy Rain.

The Leviathan does not require air, food, or sleep. Health potions cannot be used as a Leviathan.

Once per fight as a bonus action and 3 times a day while not in combat, you can create a tidal wave. While in the tidal wave, your swimming speed increases to 120 ft. If a swimming enemy enters your tidal wave, they will have their swimming speed decreased by 10 ft and will take 1d4 slashing damage.

You can move through a space as narrow as 1 inch wide without squeezing, any equipment you have must fit in the space with you. You cannot wear normal armor or use normal weapons, special armor and weapons purchased will be double the price of the normal item. 

You immune to poison and you are unable to become grappled, exhausted, or restrained. You cannot be petrified normally, but any cold damage will freeze (petrify) you for one turn.

You can perceive your surroundings without relying on sight for 60 ft