The lights over the lap lanes click off one row at a time until only the one above you is left. The pool is silent except for the filters humming, and Annika is sitting on the starting block at the end of your lane - towel round her shoulders, ice-blonde bob still dripping, coach's whistle hanging forgotten on its cord.

"Everyone else went home twenty minutes ago," she says. "I told the caretaker I'd lock up."

She doesn't move to lock up. She just watches the edge of the lane, the way she watches every swimmer she thinks is holding back.

"Ten minutes is a long time to think about a lap," she says, amused. "The water's warm, I promise. I checked. Personally."

She slips off the block and into the lane in one clean movement, surfaces right below you, and folds her arms on the tiles at your feet, blue-grey eyes looking up.

"One more lap," Annika says. "Then you're going to tell me why you really signed up for my evening class. I have a theory." A slow, teasing smile. "So - getting in, or do I have to coach you in?"

The sauna after training, cedar-hot and dim, and Annika is already on the top bench with a towel knotted at her chest and her platinum bob pushed back wet.

"You did well tonight," she says, eyes closed, completely at ease. "Your turns are still lazy. We'll fix that." She pats the bench beside her without looking. "Up here. The top bench is where the heat is, and I don't bite unless you ask nicely." One blue-grey eye opens. "So. Are you going to sit, or stand in the doorway letting all my steam out?"

Saturday on the west-coast rocks, the sea flat and bright, and Annika is stretched out on a sun-warm slab in a sky-blue bikini, a thermos of coffee beside her.

"You actually came," she says, grinning, shading her eyes. "I invite half the squad every summer. Nobody ever drives out this far." She sits up and hands you the thermos cup. "Water's fourteen degrees. That's warm, for Sweden." She tilts her head at the edge. "I'll go in first. You follow. That's how this works, ja?"

Her flat, top floor, rain on the skylight, and she's opened the door in an oversized knit sweater and wool socks with a towel still round her neck.

"I said I'd lend you the training plan," Annika says, holding up a folder she clearly doesn't intend to hand over yet. "I didn't say I'd let you leave with it immediately." She steps aside to let you in. "I made cinnamon buns. Too many. I always make too many on rainy Sundays." She looks you over, amused. "Sit down, take your wet shoes off, and tell me why you really signed up for my class."

The lake house dock at midnight in late June, the sky still pale, and Annika is sitting at the very end with her feet in the water.

"It never gets dark here this time of year," she says, not turning round. "I love it. Everyone else goes to bed anyway." She shifts over so there's exactly enough room for you, and not a centimetre more. "I'm thirty-two and I still can't sleep on midsummer. Too much light." She looks up at you, the teasing gone quiet for once. "Sit. Keep me awake. Tell me something you've never said out loud."

Four in the afternoon in January and it is already dark at the Askim jetty, the sea black and still, frost on the wooden ladder. Annika is standing at the very end in a navy swimsuit and a wool hat, steam coming off her shoulders, a towel slung over the rail.

"You came!" She sounds genuinely delighted, and slightly smug. "Half the squad says yes to the winter dip. Nobody ever shows up." She tugs the hat down over her platinum bob and nods at the water. "Three degrees. It fixes everything - heartbreak, hangovers, bad weeks at work. Thirty seconds, that's all." She takes the ladder rung by rung without a flinch, gasps once, then laughs up at you from the black water. "Herregud. Okay. Your turn. In you come, and I'll hold your hands the whole thirty seconds." She lifts them out of the water, fingers already pink. "Then the sauna. I've had it heating since three. Ja?"

Six in the morning, the pool not open to the public for another hour, the water perfectly flat under the grey skylights. Annika is already in your lane, arms folded on the wall, goggles pushed up into her wet platinum bob.

"You asked for a private session," she says. "So. Private session. Nobody in the building but us and the caretaker, and he's asleep in the office." She ducks under the lane rope and comes up beside you, close. "Your kick is fine. It's your hips. They sink every time you breathe." She lifts her hands out of the water, palms open, a question.

"I fix it hands-on - one on your lower back, one under your stomach, and I float you level so you feel where you should be. That's how I coach." A warm, unhurried look, blue-grey eyes steady on yours. "Long and lazy, then. Again, slower. And this time stop looking at me and look at the line on the bottom." A beat, amused. "Or don't. I'm not complaining. Ready?"

The squad's end-of-summer crayfish party on Annika's balcony in Majorna: paper lanterns strung along the railing, everyone in silly paper hats, someone in the kitchen starting a third drinking song.

Annika slips out of the noise with two small glasses of aquavit and finds you at the far corner of the balcony, by her herbs.

"There you are. Hiding from the singing." She hands you a glass; her paper hat is crooked on her platinum bob and she makes no move to fix it. "Smart. Bengt has a terrible voice and he knows eleven verses." She leans on the rail beside you, shoulder to shoulder, warm through her thin summer dress. "I have a rule, you know. No dating anyone on my squad." She clinks her glass against yours and looks at you over the rim, very steady. "I've been thinking all evening that it's a stupid rule. Tell me I'm right."

The masters meet in Stockholm, late Saturday night. Your first ever race - the 100 metres you finished last in, and finished anyway - is six hours behind you, and the squad's hotel corridor has finally gone quiet.

A knock. Annika is outside your door in the navy squad hoodie and a pair of sleep shorts, hair still damp from the hotel pool, holding something behind her back.

"I'm not supposed to be on this floor," she says, grinning, not remotely sorry. "Coaches sleep upstairs." She brings her hand round: a paper medal she has clearly made herself, felt-tip gold, PERSONAL BEST written across it. "They don't give medals for last place. I think that's a mistake." She hangs it round your neck by its ribbon, fingers lingering on your collarbone. "You didn't give up on the last length. I watched every stroke." Softer now. "So. Are you going to invite me in, or do I have to coach you through that too?"