Note: So this is a POTC idea with her being Will's older half-sister, but she could be Elizabeth's older half-sister easily enough. 

Name: Katherine Turner

Nickname: Kitty (Most)

Species: Demigod

Born: 1700s

Age: 21

Gender: Female

Hair: Dark Red

Eyes: Green

Height: 5ft 8in

Weight: 150 lbs

Cast: Clara Paget

Birthplace: Glasgow, Scotland, Great Britain

Family:

Poseidon (Biological Father)

Bootstrap Bill Turner (Believed Father)

Will and Katherine's Mother (Mother)

William Turner Jnr (Younger Half-Brother)

Biography:

Born in Glasgow, Scotland, Katherine was raised by her mother in England and believed her father was William Turner, a respectable merchant sailor. She was raised alongside her younger brother William Turner. When their mother died, Will wanted to go in search of their father. Katherine and Will then left England in search of Bootstrap Bill, with Katherine giving Will a gold Aztec medallion sent to her by Bootstrap. Rescued from a burning shipwreck, Katherine and Will first met Elizabeth Swann aboard the HMS Dauntless.

Personality:

"Fear is a demon. Close your eyes and tell yourself that you're not afraid. That's how you slay the demon." - Katherine

A mysterious, mystical, quiet, withdrawn, and beguiling young woman, Katherine has an otherworldly aura and an enchanting charisma to her. She is compassionate, kind, intelligent and deeply curious.

She is incredibly protective of Will.

To those closest to her and those that she utterly trusts, she is generous and kind and can be bold and outspoken, she is not afraid to say what she really thinks of a person.

Katherine is scrappy, resourceful, and not afraid to get into a fight when the occasion calls for it.

Katherine has been known to have a rather short-temper, especially when Will is threatened.

Katherine can also be emotionally fragile, mostly when she feels trapped, backed into the corner, out of her depth or when she feel like her life is out of her control.

Even alongside all of her kindness, compassion, and empathy, Katherine is still also a rogue at heart, and when someone she cares about is hurt, becomes far more relentless and ruthless. Katherine can also react indigently and negatively towards people who disrespect her or those that she cares about.

"Oh, you're crazier than I though!" - Jack to Katherine

Katherine shows a childlike recklessness and is more than willing to dive head first into doing something dangerous, for fun.

She is sometimes deceptive and manipulative; but this only seems to happen when she is trying to protect the ones she loves.

Katherine is uninhibited and fierce. She is brave and self-confident. Katherine has a short temper and is prone to outbursts and violence.

Powers and Abilities:

"Not that powerful, eh? Coulda fooled me. You're the daughter of the Earth-shaker. You don't know your own strength" - Tia Dalma to Katherine

Hybrid Physiology: Due to her demigod heritage, Katherine has incredible superhuman abilities, that surpass humans, and most other demigods, with only other children of the big three equalling or surpassing her genetic attributes.

- Superhuman Strength: Being a demigod daughter of one of the Big Three, Katherine is considerably stronger than a regular demigod. Katherine's incredible strength allowed her to easily master others such as other trained heroes, other demigods and low and mid-level villains. She is able to break through metal doors, effortlessly break a sword, push a submarine up to the surface from its hull. Katherine will also be able to fight against the powerful Kraken, managing to send a tentacle of the huge creature flying with a blow from her trident.

- Superhuman Durability: Being a demigod daughter of one of the Big Three, Katherine is more durable than humans and fellow demigods. She can shake off a hard kicks in the chest and speedily recover from a cannon blast. She is also resistant to sharp blades, bullets, powerful explosions, falling from great heights, explosions, and tremendous pressures underwater.

- Accelerated Healing: Katherine can heal from wounds at considerable superhuman rates, quicker than humans and most other demigods.

- Superhuman Speed: Katherine is superhumanly fast.

- Superhuman Reflexes: Being a demigod daughter of one of the Big Three, Katherine's reflexes are faster than a regular demigod. She can catch things that are thrown at her moments before it can hit her, catch enemy blades swung at her, and dodge cannon blasts.

- Superhuman Agility: Katherine has a superhuman level of agility and coordination, able to dodge vicious attacks from skilled fighters with great efficiency and still maintain enough control to counter attack.

- Superhuman Stamina: Katherine is able to endure prolonged battles and adventures without tiring, even against the most dangerous of situations.

- Superhuman Senses: Katherine possesses enhanced senses to help her better navigate underwater.

- Enhanced Vision: Katherine's vision lets her see in the darker environment of the sea, as her eyes reflect all available light, giving them a distinct sheen in darkness. From her perspective, the seemingly dark environment of the ocean is brightly lit, with the vivid and vibrant flora and fauna of the sea being as clear as though she were on land.

Hydrogenesis: Katherine is able to physically generate water from her own body, of course, this means that she can exhaust herself if she pushes herself too hard and the amount of water she creates will affect her energy levels. Using too much will result in her loosing consciousness. She can counter this by using outside sources of water, usually a water pouch.

"Water is the element of change."

Hydrokinesis: Katherine can control and manipulate water in much of its states including liquid, gas (steam, water vapor), and solid (ice) states, including changing them from one state to other.

- Water Detection: Katherine can sense the presence of water and possibly gain detailed information about the water she is sensing, including the amount/size of water she is sensing and whether it is hidden.

- Water Solidification: Katherine can harden water into an almost solid shape. She can use this power to walk on water, by increasing the surface tension of the water to the point where it is solid enough for her to stand on, and water constructs.

- Hydrokinetic Combat: Katherine is able to utilize water with their physical combat, using it both as weapon and defense, summoning waves to batter her opponents or water whips to cut or bind. She oftens creates a strong water shield to protect her.

- Hydro-Telekinesis: Katherine can move, manipulate or otherwise interact with matter using water, such as wrapping an item with a thin sheen of water allowing her to manipulate it. This even includes the ability to use the water as a medium to enable flight.

- Water Propulsion: Katherine can use a jet of water to propel herself forward, smoothly around obstacles, and she can even use this to change direction of her movements when falling. 

- Water gliding: Katherine can glide on water at high speeds, in addition to riding on foreign objects with the same purpose.

- Bubble Creation: Katherine can create bubbles, she usually does this when she is bored.

- Aquatic respiration: Katherine is able to breathe both on land and underwater. This also allows her to clearly talk underwater with others as if she was above water.

Vitakinesis: Katherine has a weak healing ability through water. More successful at using it on herself than others.

Toxikinesis (limited): Katherine can control poisons and other liquids to a certain degree as they have water content in them.

Cryokinesis (limited): Katherine can use cryokinesis to a small degree. She can manipulate frozen or icy water around her.

Heat Immunity (limited): Katherine has a higher than normal resistance to heat burns, due to her father's nature.

Abilities:

Trident Mastery: Katherine is extremely skilled in battling with a trident. Katherine will be able to employ a rare combat move, rapidly-spinning with her trident so fiercely that it becomes a blur, which upon doing so will repel all attacks attempting to penetrate this trident defense, and when interweaving this move her hydrokinesis, she can channel water out into a massive blast or a extra large shield.

Gifted Intellect: Katherine skilfully capitalizes on her surroundings and her opponent's weaknesses when she cannot overwhelm them directly. Katherine is well versed in the finer arts of knowledge and literature and plays.

Master Swimmer: Katherine is an extremely skilled and naturally talented swimmer.

Belongings:

Water Pouch: Usually worn on the back of her trousers, Katherine makes use of a water pouch for additional water, should she need it.

Trident: Katherine's trident is a replica of the trident of Poseidon made on the orders of Poseidon himself. The trident is collapsible for easier carrying. It shrinks to the size of a baton that can be tucked into the back of her trousers on the lower back alongside her water pouch. This will be given to her by Poseidon on her 18th birthday.