• Marine mammals can hold their breath for a longer period of time than their feral counterparts. (About an hour.)
• Some marine animals (but definitely pinnipeds) go on land, but mostly on ice flows or islands and only for a short period of time, because they would get dry skin easily.
• Characters can be depicted as feral as an art style but it doesn't mean they switch into that form or vice versa.
• Most "houses" or living spaces of animals will be on underwater mountains, seabeds, or ice shelves, even for marine mammals. They all walk on the ocean floor, sand, or any other surface, just like a person would on land. All marine mammal households have a drainage engine that drains their home of the salt water and provides it with fresh air.
• They use modern buildings and houses, with lots of ocean-ified facilities. Their technology is advanced in some aspects, but not in the field of electricity. All of their light and power for certain machinery comes from organic material. One example is of lamps, which can be a clear container filled with bio-luminescent bacteria that have to be continuously excited to create light. Otherwise, their electricity is waterproof.
• Most of them don't have visible ears, because they are very small and fin like.
• Fish and invertebrate food of carnivorous animals will mostly be depicted in their feral form. For mammal eaters, they will be depicted in a cannibalistic way.
• However, there is a lot of food processing technology, and everyone can enjoy a treat like ice cream (with milk harvested from Dugongs, the "sea-cow", and sugar extracted from brown algae) or bread (with flour grounded from brown algae), or even alcohol (fermented from algae, again.)
• Most predators live together in a town, while prey with their own towns. But there are exceptions to this that can highly depend on if there is a high killer whale population nearby, which if there is one, predator and prey may want to live together to feel safer.
• Travel can be done pretty quickly, hundreds of miles can be covered in a day especially if they're an animal that can swim fast and far. Travelers equip themselves with nomadic equipment.
• Some animals mature faster than others, but the minimum age for adulthood is still 18. Fish and invertebrates mature quickly, while marine mammals take longer.
• A lot of behavioral habits are a bit changed to fit for the modern society aspect of this marine world or to my preferences. Baleen whales stay with their mothers longer and form friendships, Some transient orca pods are bigger than they should be, animals aren't using a majority of their time eating, animals that don't have a high life expectancy are given average human life expectancies.
• But a lot of behavioral habits still apply: Baleen whales don't have large extended families, they either have only two parents or just a mother, and some siblings. Toothed whales have large extended families. Certain fishes and invertebrates are taken care of by their large community of the same species rather than directly by their parent(s). Certain solitary animals will be leaving the nest after adulthood always.
• Whales can communicate by long distance, not by telephones but by their vocalizations that can travel very far. Friends and family can call each other by sending out a signal unique to the individual they want to contact. If it eventually reaches them, they can send messages back and forth. Other whales can listen in on this conversation though, but only members of the same species can understand it unless interspecies conversations use the Common Language to talk. Other species communicate by mail, which is quick and efficient thanks to speedy fish.
Telephones are introduced later on, they are referred to as “echophones”, as they still rely on the echolocation of certain species. Thank sto echophones, the messages of the caller and recipient can be relayed much quicker and much more privately.
No stealing, No littering, No public nudity, No defamation, No destruction of the environment, Need a permit for certain activities (building buildings),
There is freedom of speech, practice, press, right to bear arms, and the right to be secured and protected in one's own house (this is especially good to prevent terrorizing killings from predators. Everyone's homes will always be a safe space.)