Shallow water marine environment refers to the neritic marine environment between the shore and the shelf break. This environment is characterized by oceanic, geological and biological conditions, as described below, and water in this environment is shallow and clear, allowing the formation of different sedimentary structures, carbonate rocks, coral reefs, and allowing certain organisms to survive and become fossils.
Marine life, sea life or ocean life is the collective ecological communities that encompass all aquatic animals, plants, algae, fungi, protists, single-celled microorganisms and associated viruses living in the saline water of marine habitats, either the sea water of marginal seas and oceans, or the brackish water of coastal wetlands, lagoons, estuaries and inland seas. As of 2023, more than 242,000 marine species have been documented, and perhaps two million marine species are yet to be documented. An average of 2,332 new species per year are being described. Marine life is studied scientifically in both marine biology and in biological oceanography.
By volume, oceans provide about 90% of the living space on Earth, and served as the cradle of life and vital biotic sanctuaries throughout Earth's geological history. The earliest known life forms evolved as anaerobic prokaryotes (archaea and bacteria) in the Archean oceans around the deep sea hydrothermal vents, before photoautotrophs appeared and allowed the microbial mats to expand into shallow water marine environments. The Great Oxygenation Event of the early Proterozoic significantly altered the marine chemistry, which likely caused a widespread anaerobe extinction event but also led to the evolution of eukaryotes through symbiogenesis between surviving anaerobes and aerobes. Complex life eventually arose out of marine eukaryotes during the Neoproterozoic, and which culminated in a large evolutionary radiation event of mostly sessile macrofaunae known as the Avalon Explosion. This was followed in the early Phanerozoic by a more prominent radiation event known as the Cambrian Explosion, where actively moving eumetazoan became prevalent. These marine life also expanded into fresh waters, where fungi and green algae that were washed ashore onto riparian areas started to take hold later during the Ordovician before rapidly expanding inland during the Silurian and Devonian, paving the way for terrestrial ecosystems to develop.
Riftia pachyptila is a marine invertebrate in the phylum of segmented worms, Annelida, which include the other "polychaete" tube worms commonly found in shallow water marine environments and coral reefs. R. pachyptila lives in the deep sea, growing on geologically active regions of the Pacific Ocean's seafloor, such as near hydrothermal vents. These vents provide a natural ambient temperature ranging from 2 to 30 degrees Celsius (36 to 86 °F), and emit large amounts of chemicals such as hydrogen sulfide, which this species can tolerate at extremely high levels. These worms can reach a length of 3 m (9 ft 10 in), and their tubular bodies have a diameter of 4 cm (1.6 in).
Historically, the genus Riftia (which only contains this species) was placed within the phyla Pogonophora and Vestimentifera. It has been informally known as the giant tube worm or the giant beardworm; however, the former name is also used for the largest living species of shipworm, Kuphus polythalamius, which is a type of bivalve (a group of molluscs which includes clams, mussels, and scallops).
Mantis shrimp are carnivorous marine crustaceans of the order Stomatopoda (from Ancient Greek στόμα (stóma) 'mouth' and πούς (poús) 'foot'). Stomatopods branched off from other members of the class Malacostraca around 400 million years ago, with more than 520 extant species of mantis shrimp known. All living species are in the suborder Unipeltata, which arose around 250 million years ago. They are among the most important predators in many shallow, tropical and subtropical marine habitats. Despite being common in their habitats, they are poorly understood, as many species spend most of their lives sheltering in burrows and holes.
Dubbed "sea locusts" by ancient Assyrians, "prawn killers" in Australia, and now sometimes referred to as "thumb splitters" due to their ability to inflict painful wounds if handled incautiously, mantis shrimp possess powerful raptorial appendages that are used to attack and kill prey either by spearing, stunning, or dismembering; the shape of these appendages are often used to classify them into groups: extant mantis shrimp either have appendages which form heavily mineralized "clubs" that can strike with great power, or they have sharp, grasping forelimbs used to swiftly seize prey (similar to those of mantises, hence their common name).
Sea pens are marine cnidarians belonging to the superfamily Pennatuloidea, which are colony-forming benthic filter feeders within the order Scleralcyonacea. The order comprises 16 families and 44 extant genera, with around 235 accepted species.
Sea pens have a cosmopolitan distribution, being found in tropical and temperate waters worldwide, from intertidal shallow waters to deep seas of more than 6,100 m (20,000 ft).
The anglerfish are ray-finned fish in the order Lophiiformes (/ˌlɒfiɪˈfɔːrmiːz/). Both the order's common and scientific name comes from the characteristic mode of predation, in which a modified dorsal fin ray acts as a lure for prey (akin to a human angler, and likened to a crest or "lophos"). The modified fin ray, with the very tip being the esca and the length of the structure the illicium, is adapted to attract specific prey items across the families of anglerfish by using different luring methods.
Anglerfish occur worldwide. The majority are bottom-dwellers, being demersal fish, while the aberrant deep-sea anglerfish are pelagic, (mostly) living high in the water column. Some live in the deep sea (such as the deep-sea anglerfish and sea toads), while others live in shallower waters, such as the frogfishes and some batfishes.