Gaza's four sewage treatment plants cannot cope with the growing population, according to Ewash, a consortium of international and local NGOs. Israel's continued blockade prevents materials needed for maintaining and upgrading the plants from reaching Gaza, it says.

People should be warned about swimming in areas close to sewage outlets, says Ghada Snunu of Ewash. But it's not easy to tell people to stop swimming. The beach is the only recreation for the majority of Gazans.

After getting sick, Sabah says she has has avoided the most contaminated areas. But most people prefer to risk illness than give up one of their few pleasures. Her father, Rajab Aby Ghanim, 37, a self-taught surfer, is proud of his daughter's prowess and is planning to introduce eight-year-old Saja, Sabah's sister, to the joys of surfing. But, he says, I have many problems with my daughters surfing. Many people criticise me. I asked my two older daughters to stop because of the community.

Sabah sometimes senses disapproval of her activities from some conservative Gazans. There is a difference [between boys and girls]. When we are swimming in the sea and men see us, they are very surprised. They tell us to get out.

When I am older, my society refuses to allow me to surf. It's shameful. I will keep surfing until then, and then I will have to stop. I will be sad, she says.

Once, she says, her 16-year-old sister to come to the beach to watch her surf. I found her sad. I said, 'You keep wishing to go back to the old days because then you could surf and swim.' She said, 'I wish those days would return.'

Her mother and aunts sometimes come to the beach to swim if no one is around. But if others start to arrive, they get out and go home. We don't want people to talk about us.

But, for now, Gaza's surfer girl is riding the waves. People are proud of us. They say, 'This is the first time we saw a girl who knows how to surf.'