'abyssal' is a correct and usable word in written English.
You can use it to refer to things that are extremely deep or profound, as in "She had an abyssal understanding of the subject matter".
Over the decade, census scientists have explored every ocean realm from near-shore waters to the abyssal plains which cover a greater area of the Earth than all its land.
He says the team have discovered between 30 and 40 new species in the past week of diving alone.Little Hercules is cruising over hydrothermal springs, abyssal muds and the rocky tops of seamounts a kind of underwater mountain that rises from the sea floor.
Little Hercules is cruising over hydrothermal springs, abyssal muds and the rocky tops of seamounts a kind of underwater mountain.
Just to the west of the mid-ocean ridge that separates South America's tectonic plate from Africa's, it is the top of a volcano which rises steeply from abyssal plains more than four kilometres below the surface of the ocean.
The abyssal grenadier has a liver that can store enough food to keep it going for 186 days if needs be.
The abyssal fauna is also sparse.
Abyssal crustaceans and fish may be blind.
Abyssal hill, small, topographically well-defined submarine hill that may rise from several metres to several hundred metres above the abyssal seafloor, in water 3,000 to 6,000 metres (10,000 to 20,000 feet) deep.
Typical abyssal hills have diameters of several to several hundred metres.
In the Atlantic Ocean, long abyssal hill provinces parallel both flanks of the Mid-Atlantic Ridge along most of its length.
A deep submarine canyon has been cut by the Indus River, which also has deposited an abyssal (i.e., deep-sea) cone of thick sediments some 535 miles (860 km) wide and 930 miles (1,500 km) long.
