The door to the sea train slid open, and the familiar smell of salt hit his face immediately. As people began to pour out, he followed along initially, flowing with the rush of the crowd, not wanting to be trampled or wind up accidentally going to the next stop because he wasn't quick enough. He heard a soft ding behind him, then a loud hiss as the sea train sealed itself airtight. Now with the crowd mostly dispersed, he began his bi-weekly ritual of turning around to watch it leave. It floated just inches from the surface of the water normally, but rose a few more inches before accelerating quickly forward. It was out of sight within seconds, leaving him almost completely alone on the platform.
Keanos, the fifth planet from the sun of the star known as TRAPPIST-1, was a majority ocean world, somewhere in the range of 99.5% to 99.9%. On a world nearly 1.6x the size of Earth, that meant that you could jump into a boat and cruise, and never so much as see a single thing resembling land, or a dry surface that wasn't man made. What little land there was to be found were rocky, jagged stalagmites sticking out from the ocean, usually far too small and thin to put anything with any real weight on it despite being made of igneous rock, and often disappearing and reappearing with the tide. The ones that were large enough to be used were occupied by ocean research outposts and platforms, manned by skeleton crews.
For the rest of the world, floating cities were erected where people lived, though not a ton for a world as large as Keanos. There were eight of these floating cities, four for each hemisphere, all more or less equidistant from one another, all roughly the size of Manhattan. That is to say, about 23 square miles, give or take a mile, and modern technological marvels. They ran on a mix of solar and geothermal energy, each city tapping into the planet's core for the majority of its energy needs. They'd thought of just about everything, all the way down to making the city capable of launching high into the air to avoid Keanos's incredibly powerful mega-storms that would sweep through somewhat regularly. Then, when the threat had passed, it could land gently as if it had never moved.
Rylan was one of about a million men and women currently living in one of these cities, better known to the people of Keanos as Sea Castle, located in the northern hemisphere. Sea Castle had one very important job, and that was to build both manned and unmanned starships and submersibles for space and ocean use. Prior to the discovery of anti-grav technology, humans were content to build their starships in space. It cost far less to ship things up via space elevator, then put them together with the help of drones, as opposed to the old way of building everything on the ground. Anti-grav technology basically allowed humans to laugh in the face of physics, and use a resource-rich planet like Keanos to its fullest. Launching extraordinarily heavy starships full of supplies suddenly became extraordinarily cheap, so building them on site where the resources were mined, refined, and then turned into things for manufacture, was the smartest thing to do.
The other cities played a role as well, usually mining operations and manufacturing. All spectacularly boring affairs, making Rylan glad that he wasn't stuck working in those industries. No, he was a marine biologist, sent to Keanos several years prior to study the ocean life in its many and varied forms. He worked with one of the aforementioned skeleton crews on a floating research station, a fairly small affair that used all of its space incredibly efficiently. Just enough room for experiments, not much room for anything else besides the absolute necessities.
Unfortunately, this was an on-week for Rylan. Marine biologists on Keanos worked on a two-in, two-out system, whereby each team of three swapped in and out every two weeks, taking some time to leave a brief for the incoming team on any changes and potential challenges for the experiments they were given, or research specimens, depending, and then were left to their own devices. He didn't really mind that he had to work in such long stints, but it was rough to make friends, or potential lovers, when you worked half of the year in two week stints.
Rylan walked across the now empty platform to a tiny little booth. Inside the booth was a slightly rusted robot assistant installed into said booth, who didn't really have much of anything from the waist down. He wasn't a fan of these particular robots as they were pretty much faceless, with minimal openings and joints, so that the salty air couldn't get into them and wreak havoc on their sensitive insides. Sadly, he had to endure talking to this thing at least twice every two weeks. Once on arrival, once on departure.
"Good morning, Mr. Larsen," came the synthesized voice of the robot. "Is it that time again? I feel like we'd seen each other only yesterday!"
Rylan sighed lightly. It was the same joke the robot made every time they interacted. Part of him wondered if it knew anything else, or if this was something other marine biologists had to endure. "I'm here to take the Blue Marine to Brava Platform. Can you summon it for me?"
"O-o-of course, Mr. Larsen. All fees are waived for employees of the Cousteau Marine Institute, as I'm sure you know."
"Yes, I'm aware," Rylan groaned lightly, pulling out a small tablet from his pocket and keying in his security code, a twenty digit sequence of numbers that only he knew, and he waited patiently. Submersible storage was often held underwater, since building upward wasn't realistic. Luckily, each submersible was sealed in its own little thick plastic bubble so as not to gain any hitchhikers. He watched as the plastic bubble rose slowly to the surface and opened. His submersible, a light blue, two person craft, was held in place by robotic arms in the bubble, allowing him to enter when the top half unsealed and slid away, allowing him access.
The Blue Marine was capable of being entered from just about any angle. Front, back, bottom, top, or sides. This was both a safety feature and a convenience, allowing the possibility of escape in emergency situations where the submersible would otherwise be trapped, while being convenient to enter based on whatever task it was being used for. The entire front half was translucent, made from a thick see through super-plastic designed to withstand crushing ocean depths. It couldn't quite go down however deep it wanted to, but generally speaking, it could easily handle depths greater than the Mariana Trench on Earth, around 11,000 meters, without so much as a creak or groan. Not that you'd want to normally on a dangerous world like Keanos.
Rylan walked forward as a small platform extended out to his submersible's plastic bubble and he carefully hopped atop the submersible waiting inside. He unsealed the hatch on top, slipped in, and closed the hatch. He double checked the seal to make sure it held, and then began a pre-dive check, a number of diagnostic scans and engine tests to ensure he wouldn't be dead in the water. When he was finished, confident the vehicle would perform as necessary, and sealed tightly within, he sent a signal to the robot up above. The bottom half of the plastic bubble slid away, and the robotic arms holding the Blue Marine dropped him unceremoniously a few feet to the water's surface below.
