As a young student holidaying in France, Julia Green stumbled across the body of a drowned boy, washed up on a beach. More than 20 years on, it's an image that still haunts the West writer. The horrific experience also provided the inspiration for her latest novel, Breathing Underwater.

"It's funny how the creative process works for a writer," Julia says as she sits down in her office at Bath Spa University, where she leads the MA in writing for young people.

"Things tend to bubble away deep in your memory, and occasionally come up to the surface in the form of a story.

"Finding the body on the beach all those years ago was one of those horrible experiences that never really leaves you."

The grisly memory has washed up in the first chapter of Breathing Underwater, when Julia's heroine Freya stumbles upon a body while holidaying in the Isles of Scilly.

"Different stories come in different ways, but the location was the starting point for this book. I've always loved the Isles of Scilly, especially St Agnes, which has been my favourite holiday destination for years.

"It's a magical place for me. When you step off the ferry and you're left there on the island, with nothing but the sound of the waves and the gulls, you feel as though you're in a place where anything could happen. Islands are like that. They have a real sense of magic.

"Like Freya, when I arrive on the jetty at St Agnes, I feel I've arrived at my favourite place on Earth. I wanted to write about St Agnes because it's such an important place for me. But in the book I've changed the name to St Ailla, just so I can have a bit of artistic licence – though anyone who knows St Agnes will recognise the place in the book, because a lot of the villages and beaches have kept their original names."

Breathing Underwater is Julia's fourth book for young people. Her previous books, Blue Moon, Baby Blue and Hunter's Heart (all published by Puffin), were all aimed at young teenagers.

"All my books are essentially about relationships," Julia says, "particularly mother-daughter relationships. It just seems to be what I keep writing about."

Julia, who lives in Bath with her husband and two teenage sons, had her big break after an inspirational writing course with children's author David Almond a decade ago.

"It was an amazing few days," Julia says. "I'd taught on many writing courses, given my role as a university lecturer, but I'd never actually signed myself up as a student on a writing course. But I'd read some of David Almond's books – Skellig was amazing – and I thought I could learn a lot from him. The course was truly inspiring, and by the end of it I'd written the first chapter of Baby Blue.

"David Almond read that first chapter, and told me that I needed to carry on and write the book and start sending it off to literary agents.

"So that's exactly what I did. I managed to get myself an agent and before long she'd found me a publishing contract with Puffin. I'll never forget the feeling of elation when I found out."

Born in Surrey, Julia's background was academic – studying the history of literature – before she returned to her childhood instinct of writing fiction.

"It was while I was studying for my M.Phil at Oxford that I started to feel there was something missing from my life – I had a need to create literature for myself, as well as studying the stuff the Victorians had written.

"I'd always written my own stories and poetry as a child, so I think I just had a natural predisposition to writing."

Later on, Julia also won a short-story competition, and was presented with her prize by the late novelist Iris Murdoch.

"It was an incredible moment," she recalls. "Iris Murdoch reached forward to shake my hand, and whispered 'it was a wonderful story, and now you must write a novel'.

"I mean, what could be more inspirational to a young writer than having that kind of affirmation from someone of the calibre of Iris Murdoch? I was over the moon."

As a lecturer in creative writing at Bath Spa, Julia has inspired many young creatives to devote their lives to children's fiction. Her students have included prize- winning writers Sally Nicholls, Marie-Louise Jensen and Elen Caldecott.

"I'm passionate about writing for children, and I'm always thrilled to see my students becoming successful after they've graduated," she says.

Breathing Underwater tells the story of Freya, who returns to the island of St Ailla searching for answers after the mysterious drowning of her brother.

"It's very much about loss and grief, but also about recovery and how we come to terms with tragedy," Julia explains. "It's a novel packed with different relationships, because that's what interests me most – how everyone has this complex web of relationships in their lives.

"Before I came to Bath Spa University, I had a spell working with so-called 'difficult' children. That is, children who had been expelled from their school. It was an amazing experience, getting an insight into the kinds of problems and trauma that some youngsters go through.

"That helped me to develop a real understanding of how children tick, and the sorts of challenges and emotions that they face, and for a children's writer, it's very important to be able to put yourself in a youngster's position."

Breathing Underwater, by Julia Green, is published on May 4, by Bloomsbury, priced £6.99.