Aquatic, lacustrine, fluvial, fluviatile, marine, oceanic, thalassic, neritic, pelagic and abyssal all refer to water and especially to a body of water but all except aquatic are highly specific in their applications and all are more or less technical terms in the geographical and biological sciences and in geology.
Aquatic may imply a habitat in water, but as applied to animals and plants it often means living in water (but not necessarily submersed) or on the water or around a body of water. It is specifically applicable to any plant (as the water hyacinth and the water lily) that has its roots in or below water.
It is also applicable to any animal that frequents the water, especially to a swimming bird or mammal (as a gull or an otter). A frog is more often described as an amphibious animal but as compared to a toad its habits may be said to be aquatic.
Lacustrine relates only to a lake; it is used in biology (lacustrine shells) (lacustrine fauna and flora), in geology (lacustrine deposits), and in archaeology.
- the lacustrine period, a prehistoric period when dwellings were erected over lakes.
Fluvial and fluviatile are used interchangeably to suggest the action, operation, or influence of flowing water though geologists perhaps somewhat prefer fluvial and biologists distinctly prefer fluviatile.
- a fluvial plain
- fluviatile communities generally have a smaller standing crop of phytoplankters
When denoting a specific relationship to a particular stream or a relation to streams as such as distinct from their action or effects fluvial is the term of choice.
- international fluvial law
- coastal and fluvial shipping
- sketched a geographical interpretation of the history of civilization through three stages: the fluvial, the thalassic, and the oceanic
—Sat. Review (London)
In reference to salt water marine (see also MARINE) is the comprehensive term, applicable not only to things that pertain to the open ocean but to those that pertain to contiguous salt or brackish waters (as bays, harbors, salt marshes, or salt ponds).
- marine shells
- marine vegetation
- marine deposits
When specific reference to the open ocean or to mid ocean is intended, oceanic is the preferred word.
- oceanic fauna
- oceanic currents
- oceanic storms
When reference is to seas or gulfs, as distinguished from the ocean, thalassic is often the term preferred especially by historians.
- thalassic empire
These terms, however, are neither so definitely restricted nor so precise as the succeeding terms, which usually name definite zones of the ocean.
Neritic refers only to the belt of shallow water surrounding a landmass.
Pelagic, which in general use implies definitely the open sea or the high seas (pelagic sealing), in its stricter technical application has reference in its extent only to the realm of the open ocean and in its depth only to so much of the water covering that expanse as is penetrable by light.
Below the pelagic zone in the deeper parts of the ocean lies the abyssal zone, where no plant life exists and animals are carnivorous and are usually blind or luminescent.