Gwen's dad is a wizard who specializes in marine magic and plants. He studies, collects and sells rare herbs and his services doing charms on ships. He met her mother while working in a small river. She was exploring under the water at the time, looking for adventure. The end result was Gwen. Unfortunately Water Nymphs can't live on land for long periods of time, so her parents never could have a real relationship. She was raise under-water by her mother with periodic visits to spend time with her father. Most part-nymphs don't show any signs of further magic, so it was expected she would learn from the water nymph community, and gow into a member of their society. Gwen was especially excited when she recieved her Hogwarts letter. As far as she could tell she hadn't shown any signs of magic, but she was glad to know she had gotten her father's magical traits. An arrangement was made for her to live with her Father while attending Hogwarts, though of course visiting her mother during the summer.
The best way to describe Gwen is bubbly. Her words flow from her mouth freely, and though she's careful of what she says, she often talks more than necessary. She can be shy around those she doesn't know...a learned trait from growing up in a hidden society, however her natural extrovert comes out easily once she know someone. She tends to be calm and levelheaded, and rarely gets upset. She has mastered the ability to breathe underwater, and loves being in or around the water whenever possible. She is an excellent swimmer, and when she's on land also tends to be graceful with her movements fluid. She doesn't mind the cold (even the snow) and generally doesn't wear shoes. Summer is her enemy as the heat makes her feel weak, exhausted, light-headed, and irritable. Even being at normal room temperatures sometimes gets to her.
Gwen has blonde hair and striking bright blue eyes. She's average height and very lean. She tends to wear as little as possible, used to needing free movement underwater, and even in winter generally has her stomach, legs, and shoulders exposed. While she doesn't dress inappropriately, she also doesn't really understand the concept of modesty either due to not needing to wear more clothing for warmth. She doesn't wear shoes (as they inhibit her ability to swim) unless she's forced.
Her blonde hair has a bluish tint to it, and if you look when she's swimming you'll see she has small gills on the side of her neck. Though difficult to see when she's not swimming, they are there upon close examination. Also, whenever she uses her symph abilities, her eyes glow blue.