The salt marshes are green this time of year and when the tide is out small white birds litter the mud like the chalk pebbles strewn across beaches further up the coast, their shrill cries trilling through the grasses. Boats on pebble-candy buoys strain against their moorings while the air holds the ghostly singing of metal lines against the mast and the ruffled flap of a pennant in the near-still breeze. Thick cold mist rolls in up the estuary, muffling sounds and blurring the edges, though it will burn off as soon as the sun comes up properly.

Damp air slows the world down until it's claustrophobic. Tankers loom through it with city blocks of cargo and the boats to the mainland shudder onwards, low side-waves shocking car-alarms into echoing voice soon swallowed and deadened by the all-consuming fog - white like a hardened cataract that everyone must peer through. Prison boats run at night and all the way through to the early morning. The only passengers are prisoners and their guards, accompanied by a few straggling alcoholics and travellers who should know better. Sometimes it feels as if the rest of you shouldn't exist. It's a little late for that now though. The boats have come in already and the pale morning light is fighting the mist.

Breathe in. The harsh sting of fresh air feels good. Set your bag down, or stand there swaying with your racing pulse. Shirt's stuck to your back, you know? So take it off. Kick your trainers off, peel cotton from skin and let the air dry your sweat. Through the woods was tough going, but you're here now, mud-splattered and aching. Or maybe you're not here at all, but I am. I'm here now, and that'll do.

Barnacles and limpets stub toes. Pebbles underfoot dig into tender skin and larger rounded ones cup the foot-arch painfully. Cold doesn't help, either. Sun isn't warm yet; it's too early. Seaweed stinks like something rotten, but I like it because it's salty and harsh. Cuttlefish are in the tide-line, tangled with nylon rope, washed up lobster pots and splintered wood. Real drift-wood is rare. Find it and you can sell it to the local artists. They'll buy anything – nearly as a bad as the tourists. There isn't much difference between them. The artists are the tourists strange enough to want to stay.

Water's icy. Waves fizz into the shingle mix that passes for sand. Larger rocks are slippy, coated in green sea-slime. Dark brown bubble-poppers and planty sea-snakes float mid way out. Get past those and it's clear all the way out and all the way down. Deep water to the buoy and maybe a little further before the currents take over. It's shorter than the Channel to the other side, but they don't swim across it here. People die in this stretch. Further up the coast the currents are calmer and the shipping lane's less busy. Here, you don't go out much beyond the buoy. Don't risk it to the shipping lane – trust me, the tankers wouldn't even see you coming.

Knee deep is bearable without thinking, but then it gets harder. New temperature is fine below the surface, but the creeping tension line of cold brings dread at it inching further. Better to jump off the sea wall and risk your fate in the foaming waves and half protruding rocks, assuming you're not a coward.

No?

So bear it out. Keep on walking and then push off and duck under. Start swimming if that's what you're here for. It's not the Atlantic- proper. It could be colder.

Start swimming! Don't splutter, just breathe. Front crawl. Salt stings. Knew it would. Not so cold anymore. Muscles warm when they work, even if skin stays pimpled. Listen to that– it's all silence. The noises are the same as before, but everything is calm. No thoughts, just left arm, right arm and kicking all the time. That's why you came. One head bobbing above the waves, and nobody else. Nobody else at all. Just the sea.

Stumble back up the beach, cold and shivering. Only the sea sucks heat out like that - leaves you exhausted and knowing you're alive. So, I've proved it for today at least, now shut up. Get dry, get dressed. If I'm late they'll ask questions. Better to save them the bother. They don't really want to know. Let Peter figure out the salt coating my skin himself, if he even cares.

Jump down on the land side of the stile and miss the mud or you'll get your shoes dirty. They're black if you're not looking for trouble with Mrs Murphy, but the mud shows up on the shiny leather anyway – all dull and dusty. Given that this is a pony paddock and out here is the wilderness compared to the town where school is, it's probably mixed with horseshit. It's not a good idea to step in anything.

The bus'll be late because this time of year the bridge over the river will be up and it'll have come the long way round, but there are only three buses a day. Can't afford to miss it, even if I have to sit here an hour. This stop is the last stop. Might as well be at the end of the world, but don't think like that. It could be worse.

People who come to this island – tourists, prisoners, old people even – come to leave, you know they do. They have a clearly defined length of stay, whether it's 'til the next tide, the next week, the next month, the next year, or until their heart gives out or their liver fails. They all come to leave. It's only the locals who don't.

We stay trapped here – not by the tides, or the currents or the mist, but we're still trapped. It gets to you – living on an island. The ones that leave almost always come back. It tells us that it's family, you see, and the patterns the land carves on us are hard to erase. It takes something big to make you realise you even want to leave at all, but I'm alright. I'm getting out as soon as I can. Watch this space and eat my dust because after this summer, I'm gone.

I sit at the bus shelter with the hood of my jumper pulled up over my head, arms hidden inside and my bag on my lap, slumped forward, dozing. Sleep is a precious thing and any other day I'd have had more of it. Good job I can sleep anywhere. Peter can't.

Peter – seventeen, just younger than me, but a little more handsome and a lot more confused - dark-haired and stupidly brutish. His uncle races horses and has never been off the island in his life. He won't leave either. It's something you can tell when you've known someone a while. Anyway, he's here. He nudges me along the bus-stop bench and I grumble but don't look up. I know it's him. He comes early like I do. No, not early like I do, early because I do. The others don't bother. A warm thigh presses against mine and my hood gets pulled down.

"You look like shit."

Keep my eyes firmly closed against the intruding light and against him and pull it back up with one hand. Besides blocking him out, this way I look half-way like an angel. "Thanks."

"Seriously."

"Yeah. I know."

He huffs, folds his arms across his chest and slumps far more convincingly than me. He's more teenage than I've ever managed. I suppose I envy that. "Whatever." Our thighs are still pressed together. He's tactile when he thinks he can be, and he can be at the moment. The Post Office isn't open yet. There's no one to see. "It's not like you're going to tell me why, anyway. Are you, Ghost Boy?"

I look up, peering at him from under the hood. "Don't call me that."

He shrugs, and his eyes sparkle. "But you are – cold as ice, pale as snow and you melt away like the bloody mist."

I shake my head, wearily straightening up so I'm not hunched over anymore. Sometimes I think he likes that idea more than he likes me. Maybe that's why I've never told him where I live. "I have a pulse, Peter."

His grin breaks to the surface and he nudges into me. "I know you do." He should. He's felt it. "Doesn't mean you're going to tell me why you look like shit, though, does it? You like to keep secrets."

I tug my hood down and force our eyes together. "That's rich coming from you." Usually I wouldn't pick a fight, but today's different. Today I need to.

He sighs again, disengaging, leaning back, but I know I got to him. His smile isn't there anymore. "Don't get yourself worked up. Lucy's going to get here any minute."

"Right," I grumble out. "Wouldn't want her to figure out you like kissing boys, now would we?" Sad thing is I'm not shouting. I'm whispering, just like he wants me to, watching for Lucy, with some part of my brain working at a plausible topic to explain away the fight. Maths homework that I won't let him copy seems to sound about right.

In a place like this – a place where there are three buses a day, a pub, a post office, a chemist and four churches, people like to know what's going on and some things aren't quite accepted. There are already reasons beyond my control that I'm not liked. It wouldn't be wise to add to them. Peter's safe at the moment and I understand why he wants to stay that way but that doesn't mean I enjoy staying quiet. If I was on the mainland, it would be different. A lot of things would be different if I was on the mainland.

"Just because you had a shit night, you're bringing all this stuff up."

I tug my hood back up. "You know me so well. We must be soul mates."

He shakes his head and makes to slide away from me to the other end of the red plastic bench, but not before grabbing my head in a practiced hold designed to look exactly like he's roughing, rather than touching me up.

That can mean only one thing: Lucy's here.

My hood slips and his lips graze my ear. Peter does theatre. He spends time thinking about what the audience sees. "Get over it Ghost Boy. Come and see me after class."

I grab his tie firmly, pushing him away from me as if I'm beyond pissed off. I'm not acting much – this is a crock of shit I don't like. I rake in his eyes and shake my head. "Can't. Got an interview. You'll have to whack yourself off."

Lucy gasps and looks away hurriedly, trying to pretend she wasn't eavesdropping. Her bright-red cheeks and the way she's staring at her painfully flat cross-bar shoes give her away though. They aren't that interesting. Poor kid is only twelve; if I was in a better mood I'd have spared her. Peter slaps my hand away, hard, voice angry and spitting. "Don't fucking touch me."

I shake my head and pull my hood back up, reaching into my bag to find battered headphones to slot into my ears. He does a good impression of a homophobic git a lot of the time. "Wouldn't dream of it, I'm sure."