A large flying craft moved swiftly across the surface of an astoundingly beautiful sea. From mid-morning onwards it plied back and forth in great widening arcs, and at last attracted the attention of the local islanders, a peaceful, sea-food loving people who gathered on the beach and squinted up into the blinding sun, trying to see what was there.

Any sophisticated knowledgeable person, who had knocked about, seen a few things, would probably have remarked on how much the craft looked like a filing cabinet - a large and recently burgled filing cabinet lying on its back with its drawers in the air and flying.

The islanders, whose experience was of a different kind, were instead struck by how little it looked like a lobster.

They chattered excitedly about its total lack of claws, its stiff unbendy back, and the fact that it seemed to experience the greatest difficulty staying on the ground. This last feature seemed particularly funny to them. They jumped up and down on the spot a lot to demonstrate to the stupid thing that they themselves found staying on the ground the easiest thing in the world.

But soon this entertainment began to pall for them. After all, since it was perfectly clear to them that the thing was not a lobster, and since their world was blessed with an abundance of things that were lobsters (a good half a dozen of which were now marching succulently up the beach towards them) they saw no reason to waste any more time on the thing but decided instead to adjourn immediately for a late lobster lunch.

At that exact moment the craft stopped suddenly in mid-air then upended itself and plunged headlong into the ocean with a great crash of spray which sent them shouting into the trees.

When they re-emerged, nervously, a few minutes later, all they were able to see was a smoothly scarred circle of water and a few gulping bubbles.

That's odd, they said to each other between mouthfuls of the best lobster to be had anywhere in the Western Galaxy, that's the second time that's happened in a year.

The craft which wasn't a lobster dived direct to a depth of two hundred feet, and hung there in the heavy blueness, while vast masses of water swayed about it. High above, where the water was magically clear, a brilliant formation of fish flashed away. Below, where the light had difficulty reaching the colour of the water sank to a dark and savage blue.

Here, at two hundred feet, the sun streamed feebly. A large, silk skinned sea-mammal rolled idly by, inspecting the craft with a kind of half-interest, as if it had half expected to find something of this kind round about here, and then it slid on up and away towards the rippling light.

The craft waited here for a minute or two, taking readings, and then descended another hundred feet. At this depth it was becoming seriously dark. After a moment or two the internal lights of the craft shut down, and in the second or so that passed before the main external beams suddenly stabbed out, the only visible light came from a small hazily illuminated pink sign which read The Beeblebrox Salvage and Really Wild Stuff Corporation.

The huge beams switched downwards, catching a vast shoal of silver fish, which swiveled away in silent panic.

In the dim control room which extended in a broad bow from the craft's blunt prow, four heads were gathered round a computer display that was analysing the very, very faint and intermittent signals that emanating from deep on the sea bed.

"That's it," said the owner of one of the heads finally.

"Can we be quite sure?" said the owner of another of the heads.

"One hundred per cent positive," replied the owner of the first head.

"You're one hundred per cent positive that the ship which is crashed on the bottom of this ocean is the ship which you said you were one hundred per cent positive could one hundred per cent positively never crash?" said the owner of the two remaining heads. "Hey," he put up two of his hands, "I'm only asking."

The two officials from the Safety and Civil Reassurance Administration responded to this with a very cold stare, but the man with the odd, or rather the even number of heads, missed it. He flung himself back on the pilot couch, opened a couple of beers - one for himself and the other also for himself - stuck his feet on the console and said "Hey, baby" through the ultra-glass at a passing fish.

"Mr. Beeblebrox...," began the shorter and less reassuring of the two officials in a low voice.

"Yup?" said Zaphod, rapping a suddenly empty can down on some of the more sensitive instruments, "you ready to dive? Let's go."

"Mr. Beeblebrox, let us make one thing perfectly clear..."

"Yeah let's," said Zaphod, "How about this for a start. Why don't you just tell me what's really on this ship."

"We have told you," said the official. "By-products."

Zaphod exchanged weary glances with himself.

"By-products," he said. "By-products of what?"

"Processes." said the official.

"What processes?"

"Processes that are perfectly safe."

"Santa Zarquana Voostra!" exclaimed both of Zaphod's heads in chorus, "so safe that you have to build a zarking fortress ship to take the by-products to the nearest black hole and tip them in! Only it doesn't get there because the pilot does a detour - is this right? - to pick up some lobster...? OK, so the guy is cool, but... I mean own up, this is barking time, this is major lunch, this is stool approaching critical mass, this is... this is... total vocabulary failure!"

"Shut up!" his right head yelled at his left, "we're flanging!"

He got a good calming grip on the remaining beer can.

"Listen guys," he resumed after a moment's peace and contemplation. The two officials had said nothing. Conversation at this level was not something to which they felt they could aspire. "I just want to know," insisted Zaphod, "what you're getting me into here."

He stabbed a finger at the intermittent readings trickling over the computer screen. They meant nothing to him but he didn't like the look of them at all. They were all squiggly with lots of long numbers and things.

"It's breaking up, is that it?" he shouted. "It's got a hold full epsilonic radiating aorist rods or something that'll fry this whole space sector for zillions of years back and it's breaking up. Is that the story? Is that what we're going down to find? Am I going to come out of that wreck with even more heads?"

"It cannot possibly be a wreck, Mr. Beeblebrox," insisted the official, "the ship is guaranteed to be perfectly safe. It cannot possibly break up"

"Then why are you so keen to go and look at it?"

"We like to look at things that are perfectly safe."

"Freeeooow!"

"Mr. Beeblebrox," said on official, patiently, "may I remind you that you have a job to do?"

"Yeah, well maybe I don't feel so keen on doing it all of a sudden. What do you think I am, completely without any moral whatsits, what are they called, those moral things?"

"Scruples?"

"Scruples, thank you, whatsoever? Well?"

The two officials waited calmly. They coughed slightly to help pass the time. Zaphod sighed a "what is the world coming to" sort of sigh to absolve himself from all blame, and swung himself round in his seat.

"Ship?" he called.

"Yup?" said the ship.

"Do what I do."

The ship thought about this for a few milliseconds and then, after double checking all the seals on its heavy duty bulkheads, it began slowly, inexorably, in the hazy blaze of its lights, to sink to the lowest depths.

Five hundred feet.

A thousand.

Two thousand.

Here, at a pressure or nearly seventy atmospheres, in the chilling depths where no light reaches, nature keeps its most heated imaginings. Two foot long nightmares loomed wildly into the bleaching light, yawned, and vanished back into the blackness.