'Kind of you.'

In a moment she said, 'I did a year in bomb disposal when I was still in England. It -'

'That was before you lost your father?'

She looked up quickly. 'Yes. Why?'

'I mean you had these -' wrong start, had these suicidal tendencies was not very flattering – 'these urges to push things to the brink quite a while ago.'

She watched me quietly and when she spoke again her voice was lower. 'I suppose so. We're a bit alike, aren't we? It used to turn me on – and this is why I mentioned it, actually, about bomb disposal – it used to give me a real kick to sort of be in their presence, just sitting quietly in front of those things, knowing how much awful power there was in them. And being close to you gives me the same feeling, I mean the tension comes off you in absolute waves. And I like that.'

She got up and took the medical kit to the other end of the cabin and put it into a cupboard and then went into the head, and this was the first chance I'd had so I went over to the phone and dialled the number.

'Yes?'

'Shadow safe.'

I left it at that and hung up. He would have had support people watching my hotel and they would have expected me there after I'd called him last night from the quay, and they'd have started worrying by first light and Ferris would have signalled the board as a matter of routine, executive missing, and that boat had made a lot of noise with all the police and everything and he might have put things together and started a search.

When Kim came back she said, 'I want you to rest for a bit longer,' and dropped a pile of magazines onto the bamboo stool, 'just till you get your colour back.'

That had been hours ago and now she was honing the knife and not talking very much. She'd gone into a kind of shell, and I didn't disturb her, spoke only when she spoke.

'Sometimes you won't see one for weeks, then you'll see a whole group, moving in to feed on something.'

Something like Roget, the black, still floating out there, unless his finger had got jammed inside the trigger guard of the big Suzi and he'd gone all the way down.

'Have you seen one today?'

'Couple of dorsal fins. Over there, look.'

Cutting the surface a hundred yards away, splinters of light flashing as they turned and caught the sun. I hadn't noticed them.

The noon heat pressed down, its weight seeming to calm the sea. The glare came up from the water blinding bright, flooding the cabin and bouncing, flashing on brasswork and reflecting in barbs of light. The silence was absolute and there was no motion except when the swell rolled under the boat; we floated here in isolation, trapped between sky and sea under the burning-glass of the sun.

'Did you expect them to be there?' I asked her.

Sound carried, and we spoke in murmurs.

'In a way, yes.' She turned the blade again on the stone. 'I've been getting a feeling, lately. A feeling it won't be long.'

I watched the two fins. I think there was a third now but the light was tricky, the whole surface shimmering. 'Before you find the one you're looking for?'

'Yes.' Looking up at me, 'Do you get feelings like that? Presentiments?'

'Yes.' It was a third fin, I could see it clearly now. 'What kind are they?'

'I'd say they're nurses. Not grey ones, but still aggressive.'

'How big?'

'Maybe three metres, fully grown. I've seen -' she broke off as the water flashed over there and a slim metallic body broke the surface. 'No, they're threshers – that one's over four metres. It was a thresher that killed him. I got a close look.' She was silent for a time, her eyes on the rhythmic stroking of the blade. 'They hunt in packs.'

'How many is a pack?'

'It varies. Anything from ten to thirty. They've got large eyes,' she said, 'green ones, like mine.' She was watching them all the time now, the knife still in her hand.

'What's attracting them?' There were more of them now.

'They come and take a look at boats, quite often. People throw garbage out of boats.'

She was sitting totally still now, her eyes on the sea, her head angled a little, the knife lying in her cupped hand, her brown legs tucked under her, the toes flexed. They were circling the whole time but slowly coming closer to the boat, and we could hear the sudden sharp splash as one of them flicked a tail, scattering white water.

Five, six of them now.

The water was clear below, and I could see the dark line of a reef running across our beam, with shadows moving as the rest of the pack circled, fathoms down.

'Could you skipper this boat if you had to, do you think?' She was speaking slowly, only half-aware of me.

'I could work it out.'

There wasn't anything I could say that would change her mind. It was her own affair.

'As I said, some people say I just want to follow my Dad, be with him again. One man, I think he was into psychiatry or something like that, said that sticking a knife into a shark was penis envy. Takes all sorts, doesn't it?'

They were close now, seven or eight of them, their bodies darkening the water just below the surface. She didn't move, looked carved out of bronze under the hot weight of the sun, the knife in her hand. It used to give me a real kick to sort of be in their presence, just sitting quietly in front of those things, knowing how much awful power there was in them.

I got out of the deck chair and stood at the rail and looked over the side. They were closer than I'd been able to see before, and one of them came right in and nosed along the beam of the boat and I felt its tremor as it grazed the timbers.

She was wiping the oil, Kim, the oil from the blade, and dropped the rag on to the stone and kept hold of the knife, moving to the rail and looking down into the water, and when she remembered me and looked up against the glare of the sun her eyes were narrowed to slits of pale green in the bronze of her face, watching me for a moment before she said, her voice clear in the unearthly quiet, 'If he's there, I'll know. I'll know the one.' Then she reached behind her and unhooked the turquoise bra and let it fall and tugged the bikini down her legs and over her long narrow feet and swung herself across the rail and broke the surface quietly, sinking as far as her head and then bringing her legs up to lie flat, just below the surface, not moving her arms or hands but only her feet, fanning with them to move away from the boat.

They were charcoal, the sharks, and she was a light bronze and of course much smaller, but she looked less alien among them than I would have imagined, floating with her body aligned to theirs as they closed in, slowing to get the measure of this other creature.

I didn't move, could not, I am sure, have moved. She was holding the knife behind her back, that is to say underneath her, so that it wouldn't flash in the light like a lure and attract their attention, and as she took a breath and turned slowly and dived the last I could see was that she was holding it in front of her now, the knife. Then she was gone.

Fear crept in me, contracting the scrotum, tightening the throat, as I watched those things from the safety of the boat, fear of them, certainly, of their huge size and their latent primitive force, and fear for her, the suddenness of her going from sight leaving a sense of shock, a sense already of loss and appalling danger, of murder down there where I couldn't see, of feasting as they closed in and their curved jaws opened and they ripped and began ravaging.

Too much, yes, too much imagination, very well, let us regain a little of our control, so forth, she must have done this before and she knows those ghastly things from long experience and all she's doing is playing with life and death and maybe putting on a show for me, proud of her obsession, flaunting it. But even so, even so, my good friend, I didn't relish this, you may well believe.