Amphibious. The dragon can breathe air and water.

Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Niánxìng. The dragon's body is always wet and viscous. That gives him advantage on saves against grapple. 

Juǎn. The dragon's body is really near the ground and his legs are short enough that he can't be knocked prone. His snake like body allow him to roll on himself immediately.

Multiattack. The dragon makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +11 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 6) piercing damage.

Claw. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 17 (2d6 + 6) slashing damage.

Tail. Melee Weapon Attack: +11 to hit, reach 20 ft., one target. Hit: 19 (2d8 + 6) bludgeoning damage.

Kāngkǎi. Each creature in physical contact with the dragon receive the capacity to breath and move freely underwater with the same effect as water breathing  and freedom of movement (Regarding moving in water only). 

Dàlàng (Recharge 5 - 6). The dragon summon a wall of water. The dragon can make the wall up to 300 feet long, 300 feet high, and 50 feet thick. The wall lasts for the duration. Each creature in that area must make a DC 18 Strength saving throw, taking 40 (8d10) bludgeoning damage on a failed save, or half as much damage on a successful one.

Watercontrol. The dragon can lower or raise the water level within 1 km radius by a maximum of 1 meter in height. 

Change Shape. The dragon magically polymorphs into a humanoid or beast that has a challenge rating no higher than its own, or back into its true form. It reverts to its true form if it dies. Any equipment it is wearing or carrying is absorbed or borne by the new form (the dragon's choice).

In a new form, the dragon retains its alignment, hit points, Hit Dice, ability to speak, proficiencies, Legendary Resistance, lair actions, and Intelligence, Wisdom, and Charisma scores, as well as this action. Its statistics and capabilities are otherwise replaced by those of the new form, except any class features or legendary actions of that form.

Yǔ. The dragon can generate storm clouds at will causing rain whenever desired.

The dragon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail attack.

Shēntǐ (Costs 2 Actions). The dragon try to roll over his enemies by throwing is body on them. Each creature within 15 feet in front of the dragon must succeed on a DC 19 Dexterity saving throw or take 17 (2d6 + 6) bludgeoning damage and be knocked prone. The dragon stand now 15 feet in the direction of the attack.