Arms wrapped tightly around my knees, hugging them to my chest, I gaze down at the waves as they reach greedily towards me, their brown fingers stretching as though they could catch hold of me and swallow me whole. Luckily the water is thick and slow, burdened with plastic and things I can hardly bear to think about. By the time it even comes close to the toes of my trainers, it's tugged away again, gurgling and moaning. I've come here often enough to know exactly where there's no chance of being caught by the ocean.

I don't even know why I come here, why it mesmerizes me so much to watch the rhythm of the water as it dances in and out. It's not exactly pretty. The sea is dirty and so thick that I can't see anything past the surface. On top of that, ugly plastic floats across it like dirty little sea monsters, ready to snatch up the tiny amount of sea life that may still survive under the gloom. It makes me shiver if I think about it too much, but I can't help myself.

I skim my fingers just above the murky brown, then shudder and withdraw as it pulses dangerously close to my skin. I know better than to touch the ocean, of course. Everyone does. It's just one of those rules that everyone knows without saying it, one of the rules that is drummed into you from the moment you're born. Touch the water, and you'll be lucky if you don't come down with some horrific disease the next day. Touch the water, and your days are immediately numbered.

According to Grandma's stories, the ocean used to be blue, with no plastic in it at all. It almost seems impossible to believe. It sounds like one of those stories grown-ups tell kids to make them believe in a broken world, before they realize that there's no such thing as magic. A blue ocean sounds just as ridiculous as Santa Claus, or the tooth fairy, or the clown my older brother used to tell me about that lived in the wardrobe. In fact, if it hadn't been for the ancient old photograph in our living room, I would have dismissed it as a stupid fairy tale long ago.

But the water in Grandma's photo is blue. It's a picture- one that doesn't move- of her when she was in her twenties. She's wearing scuba gear, swimming effortlessly through the ocean in a haze of sapphire, as though it was the sort of thing you could do any day. I can't imagine ever living like that. It sounds incredible.

The photo isn't perfect, though. Even then, plastic is floating all around her just like all the sea creature are. And I sometimes catch myself wondering, as I stare out across the brown ocean...

If we had started to save the ocean when Grandma had been young, would the ocean still be blue?