Each generation needs its own fresh images of immensity, or rather of human smallness within it.

For some, it's Earthrise from Apollo 8, perhaps the greatest photograph ever taken. For me, it always has to do with the ocean.

Long before the disappearance and subsequent search for MH 370, the southern seas conveyed a swallowing vastness that seemed out of scale and monstrous. As a boy I heard the search for a lone yachtsman in the mid-Atlantic likened not to a needle in a haystack but to looking for an umbrella in Ireland, an image that seemed absurd until I looked at the atlas. The evacuation of Tristan da Cunha in 1961 (when the island's volcano began to erupt) threw up another example that was later ironically echoed in the Pugwashian taskforce that steamed south to reclaim the Falkland Islands and South Georgia, and prove that apart from having two legs (and very good ones, according to Alan Clark), Mrs Thatcher and Captain Ahab weren't a million miles apart.

Last Man Off is set in waters still further south. Matt Lewis these days lives in Aberdeenshire and shows wildlife to schoolkids. His is a story with a "happy" ending, as one can easily judge from its first-person narration. He still owns the survival suit that helped get him off a sinking long-line fisher, but no photographs survive of his brush with immensity, only from when the survivors got ashore on South Georgia (where there is a monument to those who perished) and the Falklands.

Recently graduated, Lewis took a job as scientific observer on the Sudur Havid, a ship no larger but considerably heavier than a blue whale, built in Norway in 1964 and still plying in the southern winter of 1998 in search of Patagonian toothfish, a plug-ugly abyssal predator whose flesh sells (for twice the price of rump steak) as "Chilean sea bass" in some of the world's smarter restaurants. When the Sudur Havid set sail from Cape Town for the South Georgian fishing grounds on April 6, 1998, there were 38 men in the belly of the beast, including brothers, fathers and sons. Sixty days later Lewis was standing on the drowned bodies of shipmates on the sagging floor of a sinking life raft.

But, MH 370 aside, this is a world of rapid electronic communication and remarkably exact navigation. Though the Sudur Havid is almost a metaphor for hectic capitalism, the safety of its men seconded to profit, its distress calls were readily answered. With none of the purblind hopefulness that governed the search for Titanic survivors among northern bergs 86 years before, ships and now powerful planes converged on 55Ú56'S, 041Ú30'W. The Isla Camila steamed up and, not without further danger, Matt Lewis was taken off: as last man.

At one level, this is a story that tells itself. It is about distances, tonnages, human manifests, catch, money, survivors, each easily quantified, each easily ratioed with the others. Unlike, say, Redmond O'Hanlon, whose Trawler glimpses a similar world, Lewis is not, I suspect, a "natural" writer, if such thing there is. Neither is he a philosopher, nor does he have a particular political agenda. Because of this, Last Man Off reads as intensely true to the experience and to the sheer strangeness of being an outsider, with no real shipboard duties beyond checking hooks and looking at birds, among a multinational crew whose dynamics are impenetrable. The ship even has a ghost or "paper" captain, a super-numerary skipper there only because regulations require his ticket.

All of this Lewis delivers with plain frankness, no mocked-up emotion and no intent to demonise anyone involved, even though two crew appear to abandon their comrades at the point of maximum danger, even if captain and senior officers (Bubbles and Boetie being their unlikely names; the former dies of a presumed heart attack during the rescue) seem strangely cocooned from reality in their warm bridge cabin, in joggers and tops while everyone else struggles in oilskin.

The problems with his account are obvious enough. Lewis's point of view is limited. The first-person perspective disappears once the 21 eventual survivors are separated on to life rafts. For that part of the narrative, he has had to rely on subsequent conversations with others. Likewise the reliance on photographs of other ships and crews. But any distance in time has only lent sharpness to the account which, 16 years on, has a dreamlike precision and absence of rationale. The steady unaffected rhythm of Lewis's prose somehow recalls The Rime Of The Ancient Mariner, and perhaps it was an albatross, not this time crossbowed but caught on one of the thousands of hooks that trail behind these bizarre ships, that brought bad luck.

Lewis was on board to observe and account for the protection of birds and in the end it is the birds who prevail, as they do at the end of Moby Dick. Free of water's drowning density, able to banish distance and risk with just a stiff-winged glide, they are opportunists of a different ecological system which is indifferent to us even as we plunder it. Unlike Moby Dick or Poe's Arthur Gordon Pym, no vast whited figure appears to Lewis with a metaphysical or ecological message. Just a scream of seabirds, who gather as they always do where there is human folly and eat the dead captain's face.