Water Domain.

Gods of the water inhabit many domains, from shining seas to lakes to small forest streams. Clerics of this domain can be found commonly by seas, rivers, or lakes, whether aboard a ship or serving at a temple to bless sailors before their travels. They see the warmth, beauty, and protectiveness of water, and use their abilities to harness it to shelter others.

Level 1 Features:

Water Domain Spells.

Each domain has a list of spells—its domain spells—that you gain at the cleric levels noted in the domain description. Once you gain a domain spell, you always have it prepared, and it doesn't count against the number of spells you can prepare each day.
If you have a domain spell that doesn't appear on the cleric spell list, the spell is nonetheless a cleric spell for you.

Divine Lash.

When you choose this domain at 1st level, you learn the Water Whip cantrip, which counts as a cleric cantrip for you and doesn't count against the number of cleric cantrips you know.
You can choose use a drop of holy water as a material component for the spell, the spell deals an additional 1d6 radiant damage to fiends and undead if you do this.

Sacred Font.

Starting at 1st level, you can conjure pure holy water, taken directly from the blessed lakes and rivers of the upper planes. Over a long rest, you can conjure enough holy water to fill a number of flasks equal to your Intelligence, Wisdom or Charisma modifier (a minimum of one flask). This water lasts until you use it or complete a long rest.
A creature can use an action to drink or administer the holy water as a potion. The target regains a number of hit points equal to 1 + half your cleric level, and becomes cured of one disease or poison affecting it.

Level 2 Feature:

Channel Divinity: Water Ward.

Starting at 2nd level, you can use your Channel Divinity to release a burst of protective water.
As an action, you douse up to six creatures within 20 feet of you with blessed water. Each creature gains temporary hit points equal to your cleric level + your Intelligence, Wisdom or Charisma modifier (minimum of 1 hit point), which last for 1 hour. While a creature has these hit points, it can walk on the surface of water as if it were harmless solid ground, has resistance to acid and fire damage, and gains a +1 bonus to AC.

Level 6 Feature:

Bless Water.

Starting at 6th level, you can use your Channel Divinity to impart divine power onto water.
As an action, you present your holy symbol and choose a 20-foot-cube within 30 feet of you. For 1 minute, water in the area becomes imbued with divine energy. When a creature enters the water for the first time on a turn or starts its turn there, it regains 1 hit point if it is not a fiend or undead. A fiend or undead instead takes 2d6 radiant damage.

Level 8 Feature:

Potent Spellcasting.

Starting at 8th level, you add your Intelligence, Wisdom or Charisma modifier to the damage you deal with any cleric cantrip.

Level 17 Feature:

Rain's Blessing.

Starting at 17th level, you can use your action to summon a torrent of rain in a 30-foot-radius, 40-foot-high cylinder, which lasts for 1 minute. When you do so, you can designate any number of creatures you can see to be protected by the rain. While an affected creature is within the area, it has advantage on attack rolls, and attack rolls made against it are at disadvantage.
The rain produces water at a rate of 1 gallon of water per round in each 5-foot square area it covers when it is summoned, and again at the start of each of your turns before it ends. The water extinguishes unprotected flames and forms a puddle in the area.
If you're within 60 feet of the cylinder, you can move it up to 60 feet as a bonus action on your turn.
Once you use this feature, you must finish a long rest before you can use it again.