I'll be placing some fun lore tidbits here to store them! These mainly center around the world that Mervamp is set in and how mermaids and vampires function and interact!

General

• Mervamp is set specifically around the Fraser River in Vancouver B.C.
• Luce and her school are salmon mermaids who often frequent the shores of human populated areas.

Mermaids

• Freshwater mermaids hardly interact with saltwater mermaids. They only meet in specific areas where the two waters converge. On the other hand, there are very secluded groups of mermaids that have little interaction with other mermaids. These groups tend to live more inland.
• Freshly born mermaids look more like tiny weird fish with odd appendages. As they grow from their fry phase, they start getting more human features.
• Mermaids are frequently seen grooming each other, mostly because their hair would get so tangled from being in the water for long periods of time. They care a lot about their own appearances such as maintaining shiny scales, tangle-free hair and clean teeth.
• Hairstyles for mermaids are an individual preference, even when having loose hair in the water is a pain to manage.
• Mermaids become a common sight further up the Fraser River where there are more camping tourists, as its easier to lure humans into rivers. They also play with fishermen since they can easily gang up on one or two of them in a boat or near the water.
• Killing naive vampires is a pasttime that mermaids consider fun. They tend to play with their bodies in the water by bringing them back to the surface and watching them drop to the bottom endlessly. Eventually they get bored and sometimes even maim them permanently, only if they feel gracious enough to give vampires have a semblance of death. They don't like eating them, as they think they taste gross.
• A mermaids senses are built for living underwater. Outside of water, they are able to breathe normally like a sea mammal, but their eyesight is more fuzzy and blurred than usual. That is because their eyes have a special coating on it to see underwater, and it doesn't retract above water. They also have a worse sense of smell comparatively, as they are forced to use only their noses instead of using both their nose and mouth underwater. In actuality, they have the same sense of smell as a normal human, but to them it's a downgrade.
• Mermaid's blood taste like fish oil and have the texture of oil. Vampires find this disgusting and it's also inedible.
• Mermaids look 'half-human' not because they are half human but because of millennia of natural selection. Their species has evolved to better mimic their preferred prey, which is mainly humans. However not every type of mermaid has evolved this way, and there are still more 'fishy' type of mermaids that more closely resemble anthro fish monsters. These more 'fishy' mermaids tend to live in the deeper ocean and prey on each other and other fish instead of humans. Smaller types of fish mermaids are more shy and look more close to their fish counterparts than human and also tend to eat more from the ocean than on the shores. Mermaids who are from more brave species or frequent the shore are more likely to eat humans and look like humans.
• The skin of a mermaid dries out fairly quickly when outside of the water, which is why even though they are able to breathe above water, they stay close to a water source.
• A mermaid's lifespan is typically a little longer than a humans. They are able to live comfortably to 100 but as time goes on, their body degrades and some mermaid schools or pods cull them before they die of old age. While this is the case for salmon mermaid schools, it is not the case for whale mermaids, who often just avoid other groups all together and take care of their own until they naturally pass.
• Schools of mermaids are usually formed around fry who were born around the same time. They can meet other schools who are in the same family species as them, such as a salmon mermaid school meeting another salmon mermaid school, but they often stick together with familiarity. Mermaids only intermingle with other schools of their species socially in more neutral territory in order to lessen fights. However, meeting other schools of mermaids of another species often results in fights.

Vampires

• Vampires are only distinguished physically by their fangs and their red eyes. Mermaids often mistake them for humans because of their fuzzy eyesight.
• Vampires still maintain old traditions such as having a code of honour when performing duels. Modern duels have evolved from what they were years ago though, and are more flexible with what items are allowed and how they are performed by different covens.
• Vampires live in tight knit covens, and newly turned vampires tend to stay within the coven that houses the person who turned them.
• A vampire who is turned but not claimed by anyone becomes a wanderer, but are more at risk of attacks from other vampires.
• Vampires believe in power in numbers, and they don't remain solitary for long, feeling a desire to form a group if left alone for too long.
• Hazing is a common form of initiation within covens. The type of hazing depends on where the coven is located and what their specific traditions are, but covens that live near the water often task the initiate to kill a mermaid.
• A vampire's weight turns to the equivalent of heavy stone when put into water. If rain drops on them, they feel incredibly sluggish. If put into a lake, they'd sink to the bottom. They wouldn't die, though, unless something tears their body to pieces. The weight is only applied to them though, and if a human tried to pull a vampire up from a lake, they'd feel just as heavy as their body weight to the human.
• Vampire's are immortal in the sense that they do not age. They can sustain injuries, and if recently fed, blood does come out of them. They regenerate quite quickly, and can actually reattach limbs to themselves. If their limbs are destroyed or lost though, they do not grow new ones.