London, England (CNN) -- The planet's seas and oceans are richer and more diverse than scientists suspected, the biggest survey of marine life has revealed -- but many mysteries remain.

The Census of Marine Life, which announced its full findings Monday, has taken 10 years to complete, employing 2,700 scientists from 80 nations. The $650 million study surveyed from the coldest waters to the warmest lagoons, from the smallest microbes to the largest cetaceans.

It even looked at life 10,000 meters (6.2 miles) down in the Marianas Trench southeast of Japan.

Scientists tagged and tracked marine creatures in order to gain insight into their migratory habits and populations as well as how they breed and what they eat.

The census also explored some unusual sights during its 10 years, including what scientists labelled a "White Shark Cafe" and a "sturgeon playground" in the Pacific as well as giant bacteria and mollusks.

In August scientists working on the census revealed that the richest waters for marine life are around Australia and Japan; and that crustaceans are the biggest group populating the seas, making up around one-fifth of sea life.

Scientists estimate that there are more than 1 million marine species but only about 250,000 have been formally described in scientific literature over the centuries. Those figures exclude microbes -- of which the census estimate there are up to 1 billion kinds.

Myriam Sibuet, vice-chair of the Scientific Steering Committee on the mammoth study, said: "The census enlarged the known world. Life astonished us everywhere we looked. In the deep sea we found luxuriant communities despite extreme conditions."

The census also collated information on the 16,764 species of fish that have ever been described -- but estimates that a further 5,000 have yet to be discovered.

Central to the census is its database called the Ocean Biogeographic Information System (or OBIS), which includes 28 million observations of more than 120,000 species, going back centuries. OBIS is growing at the rate of about five million observations each year.

The amount of marine life yet to be detailed varies wildly by region. The census estimates only 10 percent is yet to be described in European waters -- but that figure rises to 75 percent for the deeper waters of the Mediterranean and 80 percent for the seas around Australia.

The census is inviting other organizations, projects and individuals to help monitor life in the world's waters by contributing to OBIS.

Ian Poiner, chair of the Census Steering Committee, said: "This cooperative international 21st century voyage has systematically defined for the first time both the known and the vast unknown, unexplored ocean.

"All surface life depends on life inside and beneath the oceans. Sea life provides half of our oxygen and a lot of our food and regulates climate. We are all citizens of the sea."

The census also used DNA barcoding -- for example, ensuring a specimen can be identified by something as small as a fish scale -- for 35,000 species, as well as establishing baseline measures so that future damage from climate change or pollution can be accurately assessed.

Patricia Miloslavich, co-senior scientist on the census, said in a statement: "Before the census, we lacked even a simple list of known marine species. Information was scattered all over the world with limited access. If we liken Earth to a firm with humankind as CEO, we must surely know the key employees and their functions."

More than 300 key scientists who worked on the census meet from Monday in London to discuss their findings and plan further work.

The survey was began 10 years ago by Fred Grassle at Rutgers University, New Jersey, and Jesse Ausubel of the Alfred P. Sloan Foundation, New York.