Your existence comes from water, so you have the option to turn your body into water at will. This is as natural to you as breathing, and can be useful if you need to fit through tight spaces. You cannot be injured in this form, but while in this form you have no way to hold anything. You can push objects but must roll a Strength check with disadvantage. 

Once per long rest, you can heal a character without spells, potions, or supplies. By using your divine energy, you can heal someone's hit points up to three-quarters of their full HP.

Outside of Combat:

You must roll a Medicine check.

DC8 or higher heals 10% of the target's total HP.

DC12 or higher heals a quarter (25%) of the target's total HP.

DC15 or higher heals half (50%) of the target's total HP.

Rolling a Nat20 heals three-quarters (75%) of the target's total HP.

One quarter (25%) of your total HP is converted into however much the target is healed. You lose 25% of your total HP.

Inside Combat:

This is your only action for your turn.

Roll a Medicine check.

DC8 or higher heals 10% of the target's total HP.

DC12 or higher heals a quarter (25%) of the target's total HP.

DC15 or higher heals half (50%) of the target's total HP.

Rolling a Nat20 heals three-quarters (75%) of the target's total HP.

One quarter (25%) of your total HP is converted into however much the target is healed. You lose 25% of your total HP.

In addition, you are weakened from this sudden energy drain and are at disadvantage (every roll) for the next two turns.

In water, your body will disassociate and join the water around you. By using your own strength and the current to push you, you can travel twice as fast as the river is flowing. You may also travel upstream, using your divine powers to communicate with the water and ease your struggle.

Because you are a water spirit, you will have difficulty moving in freezing temperatures and your base speeds are cut in half. If you remain in a frozen area for more than 24 hours, you will become frozen solid and a party member will have to thaw you out or carry you. You lose 2HP for every day you are frozen solid; once you hit 0HP you fall unconscious but are unable to turn to water. It is in this way that a naiad can be imprisoned for eternity.

Similarly, if you get too hot you will have difficulty maintaining your physical form. Around 150 degrees you will start to bubble and at boiling temperature (212) you will start to evaporate. You will recondense once you have evaporated and drifted into a cooler area. While evaporated, it is extremely difficult to control where you are going; to do so you must succeed a DC16 Dexterity saving throw with disadvantage.

You are at disadvantage for all rolls for as long as you are in these conditions. 

You have advantage on saving throws against being charmed, and magic can’t put you to sleep.

Your Nature score increases by 4 as a result of your bond with the earth.

As a result of your protective nature, your Medicine score increases by 2 but your Intimidation score decreases by 2.

Naiads reach mental and physical maturity around age 100. They are immortal for as long as there is water in their source, but they can be wounded to the point of falling unconscious. While unconscious, they will slowly heal themselves, which can take up to five years depending on the severity of the injuries. Before passing out, a naiad's mental state will determine whether they stay in their physical form (in a secure, safe place) or turn to water (in immediate danger). Once they pass out, they cannot change forms until they wake up. If they are in their physical form, they will stay where they are until they wake up, unless they are moved by an outside force. If they are in the form of water, they will absorb into the earth to find their way back to their source. Once there, the healing process is sped up exponentially. They leave their unconscious state when their body has healed itself on its own or when someone else heals them.

Quick chart of injuries and healing times:

Stabbed through with object... one week

Decapitated... one month

Lost single limb... two months

Lost multiple limbs... one year

Eaten by wild animals... five years

Ripped to pieces... five years

Naiads are fun-loving peaceful spirits. As nymph spirits, they fall under the category of Fae and as a result, they take great joy in mischievous actions, resulting in them typically landing in the gentler sides of the chaotic alignments.

A naiad's physical form can vary from five feet all to seven feet tall. Underwater, they can be as large as twenty feet tall.

Your base walking speed is 25 feet.

Your base swimming speed is 75 feet due to your abilities to travel quickly underwater.

You have lived in dark bodies of water for all of your life. You can see things in shade of gray for up to 60 feet.

You can speak, read, and write Common and Celestial, plus two other languages you have learned during the course of your long life.