haemolung through holes where the mask engaged with his collar ring, so there were no inconvenient dangling tubes. The mask itself was a simple hemisphere, the top half transparent and separated from the opaque bottom breather half. A membrane pressed against his face running in a line which centred on the tip of his nose.
'Diagnostic test,' he said.
'I am fully functional,' the suit replied in his ear, a little snootily he thought.
'Run a test anyway.'
'I just did,' it replied. 'And again.'
Entertaining a suspicion he asked, 'Are you AI?'
'Yup,' the suit replied. 'Lot of processing power in these suits nowadays and sometimes subbies like me often hitch a ride.'
'And if I don't want a submind in my suit with me?' Cormac asked.
'Aw, don't be a spoilsport.'
Cormac considered dismissing the interloper, but curiosity, and perhaps a little in the way of a loneliness he wouldn't admit, got the better of him.
'What's your name?' he asked.
'Well,' replied the mind, 'I can give you the name of the AI that made me about twenty years ago, but I prefer to be called Mackerel.'
'Then Mackerel it is.'
'Are you ready yet?' Dax leaned in through the door, also suited up. He was grinning and had a harpoon gun resting across one shoulder.
Cormac understood this utter change in his brother's character, but still felt uncomfortable with it. He pulled the mask from his face and the hood back off his head, stooped and took up his flippers, then headed for the door.
'Are you allowed to use a harpoon,' he enquired.
'Special dispensation,' Dax spoke over his shoulder as he headed for the water locks of this section of the hotel. 'There's a lot of very large g-mod turbot out there. If I get one the hotel will cook some of it for us and pay us for the rest—or rather take the cost off our bill.'
As he followed his brother he looked round for his mother, expecting her to be here to see them off. No sign of her, but then lately when she wasn't talking to Dax she was often ensconced alone in her room.
The corridor doglegged at the end and along one wall were three pressure doors with windows spaced between them. Halting by the first door Dax turned to Cormac.
'Let's take a look at your suit,' he said.
Cormac grimaced in annoyance, since he felt himself more than capable of checking out his own suit. Really, having an adult check your suit was the kind of thing that needed to be done for infants. He held up his arm, showing the small screen attached to his wrist. Dax waved it away.
'Put your mask on and your hood up, and put on your flippers,' he said.
Cormac obliged, while Dax did the same.
'Your suit is fine,' said his brother, turning towards the pressure door. Of course, Cormac's was a child's suit and would have a computing channel open directly to his brother's. If there was any problem with Cormac's suit, Dax would receive an alert at the same time as Cormac did.
The inner pressure door opened with a slight hiss of equalizing pressure and Cormac noted a change since the last time he had been here: the door that opened into the sea, which had once been made of ceramal, had now been replaced with chainglass, which made the whole experience of going through the lock a lot less claustrophobic. They both stepped inside and the door drew shut behind them. Immediately, seawater began pouring in through nozzles set in the walls. Cormac remembered with some embarrassment how frightened and helpless he had felt when he first experienced this.
In moments the water was up to his knees, then up to his waist.
'We'll head straight out to flat sands above the reefs,' said Dax, his voice clear through the phones in the plugs filling Cormac's ears. 'The turbot are out that way hunting mackerel.'
'Nasty turbots,' said the submind, Mackerel.
Cormac glanced at his brother, but Dax showed no sign of having heard the submind speak. 'Don't worry,' said Mackerel, obviously guessing what Cormac was thinking. 'I'm not letting him hear me and I won't let him hear any replies you make to me… unless of course you want me to?'
'No, keep our conversations private.'
'Thought that's what you'd want.'
The water reached his neck, then was soon over his head. It occurred to him then to wonder about what the submind had just said.
'How… will you know?'
'How will I know when you're speaking to me and not to your brother?' it said to him. 'Remember, I'm your suit and I'm monitoring you on many different levels.'
Cormac wasn't sure if he liked the idea.
A clear bell tone rang in the airlock and the water swirled around them as Dax pushed open the chainglass door.
'Let's go,' he called, something odd in his voice.
Dax pushed off and drifted out into the sea, his suit immediately adjusting to give him negative buoyancy. Cormac peered down at the bottom twenty feet below, rocky and forested with weed, mussel beds lying between like spills of coal. As he pushed off he dislodged something from a ledge below the door and turned over on his back for a moment to observe a scallop jetting unevenly away from him. Now, in this position, he gazed back at what he could see of Tritonia. On either side the convex wall curved away, filled with viewing windows, many of them lit from inside and crowded about outside with undersea life attracted to the light. To his right he saw a robot crawling along the exterior of the structure, a clean trail behind it as it stripped away barnacles, a shoal of fish dogging its course as they tucked in to the bounty of shredded shellfish it provided. The machine looked like a large aluminium lizard with a wide flat head and a mouth like a manta ray's. It wasn't something that could be mistaken for a large iron scorpion. Cormac now focused on the undersea city's roof. Up there a secondary seabed had been provided and upon this had burgeoned a forest of kelp. He knew that now, up there about the numerous artificial islands and moorings, sea otters had become established, feasting on a cornucopia of abalone.
'Come on sea slug!' shouted Dax. 'Shift yourself!'
Cormac rolled over again and kicked hard after his brother, who was lower down now, sculling over a bed of oysters and menacing a large edible crab with the barbed point of his harpoon. Once he saw Cormac coming after him, he kicked away above the crab, which held its claw high and scuttled backwards, falling over the edge of the oyster bed. Crab had been a menu favourite for over thirty years and despite the availability of the big GM sea farm versions, demand still outstripped supply. Cormac peered down at the crustacean as it righted itself and now raised its claws threateningly. It did look very much like one of the Prador, the difference being size, intelligence, and who was likely to eat who, though there had been news stories buzzing around the nets of some human soldiers trying a new addition to their diets. It was only fair, Cormac thought, the Prador showed no reluctance in adding humans to their menus.
The start of the reefs was marked by the Tesco III, which had been sunk by an eco-terrorist cruise missile over two hundred and fifty years ago. This had been during the time when Middle Eastern oil was both running out and being supplanted by fusion power. Cormac had studied some of the history of the time but found it boring in its repetition of idiocies stemming from the political corruption of science. The two-mile-long oil tanker was only vaguely recognisable as a ship under the masses of marine growth. Along one side was an entrance for divers who found such a claustrophobic environment enticing and who might enjoy hunting the massive conger eels that haunted the huge dark spaces inside. Dax increased his buoyancy and abruptly rose beside the wall of this tanker.
'Take me up,' said Cormac, then abruptly felt himself rising too. As he went up he felt the breathing-assist of the suit beginning to slacken off as pressure decreased. He also felt other subtle adjustments as it sought to protect him from the pressure change.
He swam in closer to the cliff and studied the corals and multicoloured blooms of weed that owed their existence to a craze, over a century ago, for seawater fish tanks containing colourful GM seaweeds. Amidst these
