Post apocalyptic science based story

This story takes place in our world around the year 2116.

Global warming couldn't be avoided and a runnaway effect suddenlty started increasing temperatures much faster than experts predicted. Over a few decades, temperatures rised so dramatically and quickly that most of the landmasses started turning into deserts.

Agriculture yields collapsed and most civilizations started falling appart. The only habitable landmass were the coastlines of the South Pole and some coasts in northern Canada, Nordic countries and Russia. Countries initially peacefully started to gather there but the unavoidable happened. A war over the control of these areas started. The war ended up nuclear and most countries collapsed. The following multi year nuclear winter was the final blow for most humans and land animals. Most land animals are exctinct because of desertification and the nuclear war. Radiations levels are quite high but some areas were spared by the nuclear war. Some humans still managed to survive. Only small mamals and insect live on land. There are no serious predators to humans on land but no food can be grown and hunting gathering in the desert in not viable.

decades after the end of the nuclear winter, humanity fell backwards and humans can be found in the following locations:

-desert Oasis. There are still some oasis scattered on the continents. Some of them have radiation levels low enough for humans to survive. Their water come from underground freshwater reserves. Finding food around an oasis is extremely difficult. Oasis people's diet is mostly based on the crop they grow with the water from the oasis and insects. Life in the desert is hard and some hostile groups have turned to cannibalism to feed themselve. Life in the desert is mostly like in Mad Max.

-Legendary paradise island. A few island in the ocean were spared by the nuclear war and have some freshwater source in them. Those lucky enough to live there can live from fishing and farming. These islands are extremely rare. Most humans think these island are legends but they do actually exist.

-floating cities like in Waterworld. Some groups spend their entire life living on boats wandering on the sea. Most of those groups were living on the coast and went on a journey hoping to find a legendary paradise Island. Those boats are built with a mix of scavenged materials and wood. Those humans survive by driking rainwater and eating fish but their life is quite difficult. When their boats are damaged, it s very difficult for them to fix since trees are becoming exctinct and scavenging from broken machines is becoming more and more difficult. Encounters between those groups on the sea are usually violent as each group will try to steal the other group's ship. Most of these groups die either because their ship sinks or they get attacked by another group and loose the fight.

-coastal cities. Most of humanity lives on settlements along the coasts. Some coastal areas were spared by the nuclear war and radiations levels are not too high. Humans found a way to survive in those devastated cities. They spend most of their active time on the sea fishing. Animal life in the sea coped better with global warming and was spared from the nuclear war. Some coasts are blessed with regular rainwater. In the beginning some of it was used for agriculture but as these settlement grew, most of the rain water is used for drinking and food almost entirely comes from fishing. Cities are occasianally attacked by "barbarians" coming from desert Oasis. The technology level in these cities is similar to that at the beginning of the industrial revolution. Some scavenged engines still work, there is a bit of electricity from scavenged solar panels and wind turbines. Most computers are broken. Those that still work are not really of any use in this world and are scavenged for metal. Most boat are Sailboats. Some rusty firearms still work and are quite rare. Bullets are the most highly sought after commodity. Most people use Bows, Crossbows, Swords and Pikes when they fight.

-government nuclear shelter: when it was clear that the war would eventually degenerate in a nuclear war, most governments started building gigantic underground nuclear shelters in a haste. When the nuclear war started, most of these sheleters were not completed on time.

There were other nuclear shelter around the world but they all disappeard becaus they either didn't survive the nucelar war,didn't survive the nuclear winter, were not sustainable enough and had to be abandoned or were found by "barbarians" from the desert and sacked.

Area 52 is the only shelter with modern technology left on earth. Only one of them was completed and that s the main focus of our story. The US Area 52 nuclear shelter is built 250 meters deep underground next to a gigantic underwater fresh water reserve and is entierly self sustained. It s powered by a nuclear reactor and has enough uranium to run for centuries. Diet is mostly based on vegetables and tofu for protein that are produced with the water from the underwater reserve and artificial light produced by the nuclear reactor. It has a population of around 1000 inhabitants mostly composed of government people,army officiers, doctors, biologists and engineers. The population of the shelter has a partial understanding of the situation on the surface. Their site is based in the USA. The US, Russia and China were the most hardly hit during the nuclear war and most of the land in those two defunct nations are highly radioactive. On top of that, the Area 52 shelter location was approximatively know by foreigh coutries and the target of sustained nuclear attacks. Because of that, the area around the shelter so extremely radioactive that the inhabitants of the shelter can't venture out of it for very long, even with protection. No human settlement is to be found for hundreds of miles around the site. Most of the sattelites orbiting earth were destroyed during the war but luckily one observartion sattelite survived. Using that sattelites and a few observation drones they figured out that some human settlements were founded along the non radioactive coastlines. They are unaware of the existence of desert Oasis, floating cities and paradise island. Although they really tried hard, they were unable to contact any other nuclear shelter.

It was unanimously decided that: 1) the population in the shelter would work towards finding a way for humanity to survive in this new hostile world using science 2) it would be better to stay hidden and avoid contact with humans on the surface as the discovery of their shelter would probably trigger invasion and destroy any hope of achieving 1).

Desperate to save humanity, Scientists tried to using their genetic engineering skills to modify our species and help it survive this new world. They decided that the best way to save humanity would be to modify our DNA to adapt it to this new environment, to fast forward the survavival by the fittest mechanism. Luckily a gigantic scientific database was available in the shelter and research on genetic engineering was feasible (at a very slow pace). Since the story happens about 100 years from now, even a relatively small lab with limited ressources can still achieve some things.

The first achievement was to modify our genes to make humans more resistant to radiation. Thanks to this modification, humans could "survive" in relatively highly irradiated areas. However scientists wanted to do more than that as finding food and water on land was almost impossible.

They turned their eye to the sea as the oceans were not as severely impacted as continents by the global warming and nuclear war. Ideally they wanted to turn humans into something like a fish but technology and ressources were not advanced enough to be able to give us gills as that would involve to many genes. However turning us into "sea mamals" was within reach. Genetic engineers studied the gene pool of dolphins, sea otters and similar animals that was stored in the database. After about 100 year of trial and error, hard work and many failed attempt. They finally managed to create a new race of human "home sapiens sapiens aquatilium" , quite similar to us but with the following differences

• ability to drink salt water. By modifying some genes from the Kidneys, the body is know able drink salt water and filter out salt.
• ability to metabolize water from ingested food, the body is able to efficiently metabolize and extract a lot of water from the food we eat
• ability to hold breath for extended period (30 min), by increasing the blood cell concentration and increasing the efficiency of the muscles we can hold much longer without breathing
• ability to float on the surface, by increasing the fat percentage and lung size, we can float without movingon the surface of the sea. That to allows us to sleep on the surface of the ocean.
• ability to withstand cold water temperatures. Increasing the fat percentage also makes us more resitant to the increased thermal conductivity of water vs air. We can live in water without freezing to death.
• palm hand and feet, helps to swim faster
• water resistant eyes, the surface of the eye is slightly modified and eyes can stay open in water without being damaged
• ability to deep dive up to 70 meter for a few minutes. Various modifications to our ears, nose and blood circulation system help us cope better with a deepwater diving. This allows foraging for food in deep water.

These humans look very similar to us as most of the gene modification don't drastially alter the appearance. They look very fat, have smaller ear and nose holes. They have skin connecting the fingers from their hand and feet. That s about it. From far away they look normal.

These modifications allow "home sapiens sapiens aquatilium" to forage food underwater and sleep on the surfance of the sea when necessary.

Equipped with these new genes, resistant against radiation and able to live on the sea, after a century of isolation the population of the Area 52 shelter finally decides to opens the hatch and send the first generation of "home sapiens sapiens aquatilium" into the open world. Their mission is to explore the open world and come back in a year to report. That s when our story begins.

Is that a decent base for a story? What do you think could be improved? What do you think will happen to the first generation of "homo sapiens sapiens aquatilium" when they meet other normal humans.