In the future Miami is mostly underwater. The high rises are still usable but all the buildings under 2 stories are submerged. People live and work in the city but are only able to get around by boat or helicopter. Supplies are limited - people have created gardens on rooftops and balconies. Food and water are scarce due to the lack of outside contact.
Conflict - a hurricane is being tracked and will possibly make landfall at Miami. It's a category 5+. Hurricane status was never updated so the rating 5+ means that a storm making landfall on this scale pretty much wipes the slate clean. Since Miami is already a floating city, this scale of hurricane will blow down the buildings above the water line.
People who have the means are evacuating, leaving everything they have behind. Those without means are radioing for help, but no one has responded. They track the hurricane of their computers and video screens but not one mentions the people who are trapped in the city.
Finally a small ship arrives to try to rescue some of the remaining population but will only be able to save a fraction of the trapped people. The eldest choose to stay but the rest are trying to decide how to choose those who will go. A lottery is considered but there isn't time to implement. Those with children will be the first to get on the boat. If there is room after the families are on board, they will allow those closest to also board.
The main character - Molly is a marine biologist. She studies the ocean life and how the rising ocean waters have affected their habitats. She is stranded in Miami when the hurricane warnings come out. She was part of a scientific group but was cut off from them and missed the evacuation. She meets an engineer who thinks they might survive below the water level if they can seal themselves in the building. There is a chance that they might never get out if the water level rises to high or the building they take refuge in is destroyed.