Image copyright WORMS Image caption Stargazer: The new mysid shrimp appears as though it is always looking up

A mammoth effort to catalogue all known ocean life is nearly complete.

It has taken taxonomic experts eight years to pull together all existing databases and compile one super-definitive list, known as the World Register of Marine Species (WoRMS).

Of the 419,000 species names recorded in the scientific literature, nearly half (190,400) have been shown to be duplicate entries.

One species of sea snail even had 113 different names.

The WoRMS editors have now put the number of species known to science at 228,450.

The vast majority - 86% or about 195,000 species - are animals.

These include just over 18,000 species of fish described since the mid-1700s, more than 1,800 sea stars, 816 squids, 93 whales and dolphins and 8,900 clams and other bivalves.

The remainder of the register is made up of kelp, seaweeds and other plants, bacteria, viruses, fungi and single-cell organisms.

Image copyright WORMS Image caption Littorina saxatilis - aka the rough periwinkle - was duplicated many times in previous databases

Although the definitive list has shrunk in the process of compiling WoRMS, the catalogue continues to grow rapidly.

In 2014, 1,451 new-to-science marine creatures were added to the register. It is estimated another 10,000 or more new species are held in laboratories around the world just waiting to be described.

Dr Jan Mees is from the Flanders Marine Institute (VLIZ) in Belgium, and a co-chair of WoRMS.

He told BBC News: "The purpose of WoRMS was to create a master list of all organisms that have ever been observed and described in the world oceans.

"This task is now near completion. All the historical data have been entered in the database; all the names that have become redundant over time have also been identified and documented.

“And now we have a system in place that can be used as a backbone for data management activities and for marine biodiversity research; and that can be updated by a consortium of taxonomists."

Asked to name his favourite species in the list, Dr Mees pointed to the “stargazing” shrimp (Mysidopsis zsilaveczi) in South Africa. It is so called because its eyes appear to be fixed in an upward-looking direction.

“The pigment pattern of the eyes gives the impression that animal is constantly gazing skywards. It’s not; it’s just an effect. But it’s beautiful.

"But then I would say that, because as well as being a member of the scientific steering committee for WoRMS, I’m also the taxonomic editor for the mysid shrimps.”

Image copyright WORMS Image caption Newcomers: Phoronis emigi - the first new horseshoe worm discovered in over 60 years

Image copyright WORMS Image caption Keesingia gigas, a new species of giant jellyfish - venomous and tentacle-free

Image copyright WORMS Image caption Sousa sahulensis - one of two new dolphin species added to the register

Image copyright Worms Image caption Histiophryne psychedelica: A new Indonesian frogfish. Most of the entries in the register are animals

Image copyright WORMS Image caption Nitzschia bizertensis, on the other hand, is a toxic alga

Jonathan.Amos-INTERNET@bbc.co.uk and follow me on Twitter: @BBCAmos