In the ocean where life first originated, life has the greatest impact. 242300 species of marine animals have been discovered to date and countless more are yet to be discovered. And their population is almost infinite. Thousands upon billions of marine life are believed to exist. Most of these are invertebrates or marine small organisms that cannot be seen with the naked eye but can only be felt.

According to our long research, Marine animals are mainly divided into eight groups Structurally, They are Mammals, Invertebrates, Amphibians, Reptiles, Fishes, Plankton, Plants, and Microorganisms:
Mammals

Examples: Whales, dolphins, seals, sea lions, manatees, Polar Bears and Sea Otters, Dugongs, Belugas, Narwhals.

Invertebrates

Examples: Jellyfish, corals, sponges, molluscs (e.g., octopuses, squids, snails), crustaceans (e.g., crabs, shrimp), worms, and others.

Amphibians

Examples: Axolotol, frogs, Caecilians, Japanese giant Salamanders, Greater siren and Rhinella marina

Reptiles

Examples: Sea turtles, sea snakes, crocodiles, snakes, lizards.

Fishes

Examples: bony fish like tuna, cod, mackerel and cartilaginous fish sharks rays.

Plankton

Examples: Phytoplankton (plant-like organisms), zooplankton (animal-like organisms).

Plants

Examples: Marine algae like kelp, seaweed, phytoplankton.

Bacteria, Archaea, Protists, and Viruses

Examples: Pseudomonas sp., Vibrio sp., Achromobacter sp., Flavobacterium sp. and Micrococcus sp

Marine life mainly uses gills, long lung lobes, hollow respiratory tubes, thin filaments, skin respiration, blood-lined sacs, and oxygenators for their respiration process, all of which facilitate aerobic respiration. Additionally, some organisms adapted to their marine environment with different oxygen levels may perform collective anaerobes amnioric respiration.

Gills: Fish like tuna and sharks breathe by extracting oxygen from water through their gills, which are like filters on the sides of their heads.

Lungs with Long Regions: This process is for marine mammals, which have lungs like humans. But, this lung is too wide, by which animals such as whales to inhale and store in the lungs for long periods.

Hollow Breathing Tubes: This process is for marine Invertebrates, whose has a hollow breathing tube that helps them take oxygen from the surface.

Thin Filaments: Sea Cucumber and Sea Worms have thin filaments in their gills that help them collect oxygen.

Cutaneous Respiration: This process is for marine reptiles like sea turtles can absorb oxygen through their skin while they're underwater.

Blood-vessel-lined Sacs: Marine mollusca such as octopus and squid have sacs lined with blood vessels that help them take oxygen from water.

Oxygen Diffusion Process: This process of respiration is found in marine Microorganisms or small fishes, it helps them take oxygen molecules directly throw their body.

Anaerobic Respiration: It is the most unique respiration process found in some bacteria and archaea, in which Oxygen is not the respiration component but rather some components of global nitrogen iron sulphur and carbon.

Facultative Anaerobes:It is suitable for some microorganisms of fungi or protists, allowing them to voluntary respiration in aerobic or anaerobic respiration based on the environment.

Communication systems make a powerful contribution to one's survival in an environment. All species of animals can communicate, but the communication systems of lower and higher species differ greatly. Other than humans, no other animal species is used to such advanced communication systems. About 81% of animal communication involves noise or no sounds (very low-level communication systems). Generally lower species only communicate during danger, sexual arousal, or food needs.

Marine animals communicate through sight, sound, tactile, electrical, chemical, body language, and molecular means.

sound

Whale and Dolphins: Cetaceans, including whales, dolphins, and porpoises, are the most well-known marine animals for using sounds. They produce a variety of vocalizations, including clicks, whistles, and pulsing calls.
Marine Mammals:Seal and Sea Lions
Fishes: Some species of marine fish also produce low-frequency muffled sounds to signal detection, danger, etc.
crustaceans: Some species of crustaceans also produce low-frequency sounds for communication or self-defence in times of danger.
Invertebrates: Many marine invertebrates like octopuses, and squid

Sight

Cephalopods: Which animals have higly visual power like octopuses, squids.
Marine Mammals: Which animals have well-developed eyesight, they communicate through body language and facial expressions.
Fishes: Some species of fishes communicate throw their body movements, displaying colour etc. Like clownfish.

Tactile

Cetaceans: Which animals have higly visual power like octopuses, squids, they communicate with changing color, pattern, body posture.
Pinnipeds Which animals have well-developed eyesight, they communicate through body language and facial expressions.
Crustaceans: Some species of fishes communicate throw their body movements, displaying colour etc. Like clownfish.
Crustaceans: Some species of fishes communicate throw their body movements, displaying colour etc. Like clownfish.