Wheeze honk: These are animal vocalizations most notably observed in hippos.

SCPD: This is short for Seren City Police Department.

Astaxanthin: A red pigment that belongs to a group of chemicals called carotenoids, which give color to carrots and flamingos. Astaxanthin occurs in some algae and causes the pink-red color in salmon.

Iyo: A versatile Sinhalese word that could be used to express sadness, sympathy, regret, horror, surprise, amusement and more emotions.

Pow: A Sinhalese word that comes from the idea of bad karma. In everyday speech, it can be used similar to "poor". E.g. Pow ey lamaya ("that poor child"). It can also be used when describing an act that is mean or evil.

Aney: A common Sinhalese word that could be used to convey sympathy or "please". It can also be used sarcastically.

Samanalaya: A Sinhalese word meaning butterfly.

Doppler effect: The change in frequency of a wave in relation to an observer who is moving relative to the wave source. When a car is approaching, its sound rises in pitch.

Ultra-black: Something that is ultra-black barely reflects any color at all. BMW has a car like this—Vantablack, the darkest car in the world.

Blackdragon: The Pacific blackdragon is a deep-sea fish that is known for its ultra-black color and bioluminescent displays. It's so black that it's practically invisible.

Acoustic modem: An acoustic modem is used to transmit data underwater. It converts digital data into underwater sound signals. These signals are then received by a second acoustic modem and converted back into digital data.

Poosa: The Sinhalese word for a cat.

Kos: The Sinhalese word for young jackfruit that is used to make dishes like kiri kos (milky jackfruit curry) and kos mallung (jackfruit coconut sambol).

Hemisphere: This refers to the brain hemisphere. Marine mammals such as dolphins breathe voluntarily. If they sleep like land animals, they will die of asphyxiation. Because of this, they sleep with one eye open, and only one side of the brain sleeps at a time. They also use power naps. Merpeople have similar adaptations.

King coconut: A type of large, orange coconuts native to Sri Lanka. Its sweet water is a popular drink.

Machang: A friendly way to address a male in Sinhalese.

Kinduri: The name of the large stern trawler in the story—also called a factory trawler. It has a stern ramp and rope winches to haul in a gigantic catch. The name Kinduri means "mermaid" in Sinhalese.

Kottu: A dish of diced roti stir-fried with various ingredients. It's eaten widely in Serendiva, and in the real world, it's a popular street food in Sri Lanka.

Superstructure: The part of the ship that is above deck. It includes the bridge and cabins.

Endera: An underground organization of rebels in Serendiva with a marine conservation wing. Their naval wing is inspired by a real ocean conservation organization called Sea Shepherd. Endera means "shepherd" in Sinhalese.

Dawn chorus: Fish in coral reefs sing a dawn chorus similar to birds.

Buva: The second highest rank in Calliathron's military. The title is derived from legendary mer-giants of Callian folklore. In the real world, buva means "badass" in Sinhalese.

Marabuva: The highest rank in Calliathron's military. This title is currently held by Talmus Mora, the commander of the Second Ocean War and later, the Battle of Seren City. In Sinhalese, marabuva would mean "great badass" or "killer badass" depending on how it's pronounced.

Particle beam weapons: These weapons use high-energy beams of atomic and subatomic particles such as protons and ions. Calliathron has developed AFVs that come equipped with these. In the real world, particle beams are used in particle accelerators for research (such as the Large Hadron Collider).

Blue hole: A large marine cavern or sinkhole. It's a steep, circular depression that may be hundreds of meters deep and is open to the surface. It appears as a dark blue circle in the water.

Mizukami: A mini fighter submarine (also called midget submarine) used by Calliathron's military. The name comes from the Japanese mizu ("water") and kami ("god").

Scud bots: Minuscule flying robots used by the Callian military. Scuds, also called amphipods, are tiny crustaceans. They are the marine equivalent of bees, since they help pollinate seagrass.

Mosasaur class: This is a type of massive, nuclear-powered submarine built by Calliathron—the largest in their arsenal. It can launch ballistic missiles with nuclear warheads from a distance of 5,000 km. It's named after the mosasaur, a huge marine reptile from the Cretaceous Period.

Remora: A fish that can attach itself to bigger animals such as whales, sharks and turtles. It's also called a suckerfish.

Pellets: Plastic pellets, also known as pre-production pellets or nurdles, are the building blocks of almost every product made of plastic. Marine plastic waste can be collected, recycled and made into pellets to manufacture goods.

Operation Maduva: The name of the Callian military's covert operation to Kadol Doova. Maduva means "stingray" in Sinhalese.

Exoskeletons: Computer-controlled wearable machines that can increase a soldier's mobility, strength and endurance. The technology is essentially a wearable robot. Calliathron's exoskeletons come in the form of "carapaces" and battle helmets with augmented reality. Only prototypes of military exoskeletons exist in the real world.

APC: An abbreviation of "armored personnel carrier". Calliathron has manufactured amphibious APCs to fight Serendiva.

EMP: This is short for "electromagnetic pulse". An EMP weapon creates a powerful electromagnetic field, which is capable of short-circuiting a wide range of electronic equipment. In the story, EMP guns are used to neutralize Callian scud bots.

Davit: A small crane aboard a ship. It's used to suspend and lower lifeboats or speedboats.

EMS Valakula: This is Endera's ship. EMS stands for "Endera Motor Vessel". Valakula means "cloud" in Sinhalese.

Kottamalli: This is the Sinhalese word for coriander. It's often brewed into a hot drink—a traditional home remedy for cold and other ailments.

Mechwalker: Short for mechanized walker. It's still an experimental vehicle concept.

Flamingo Mk II: The mechwalker-Cypod hybrid that Anuk Abeykoon prototypes in the story. The bipedal design is inspired by a flamingo. It comes equipped with a railgun and a robotic arm. Mark I or Mark 1 often refers to the first version of a weapon or military vehicle.

Railgun: These guns use electricity and magnetism to shoot projectiles instead of pressure from ignited gunpowder. Railguns can shoot projectiles to reach speeds of 8,850 km/h (Mach 7)—over twice that of the fastest traditional bullets. They pack in so much destructive kinetic energy that they don't need explosives. Since they don't need to carry propellant and explosives, they are cheaper to make and safer to store and transport. This is particularly advantageous at sea, since an accidental explosion can destroy an entire ship. They are not used widely in the real world.

Marine Drive: A freeway that runs along the coast in Seren City's administrative district. It passes by the prime minister's secretariat, Square and park.

AFV: Acronym of "armored fighting vehicle".

SAM: Acronym of "surface-to-air missile".

Immortal jellyfish: A small, biologically immortal jellyfish also known as Turritopsis dohrnii. When it's exposed to stress, physical assault or is sick or old, it can revert to its polyp stage. This is akin to a butterfly reverting to its caterpillar form. This process can go on indefinitely, rendering the jellyfish biologically immortal.