A 70,000 mile journey of French research ship has discovered one million new species- many of them never seen before by man - as it crossed the Atlantic, Pacific, Southern and Indian oceans.
Among the most eye-catching was the siphonophore, the world's longest animal that can extend for up to 150ft, bristling with poisonous tentacles.
It lurks about 3,000ft below the surface of the sea trapping prawns and shrimps in its poisonous tentacles.
Other creatures include what look like brightly coloured sea centipedes, ghostly fish and technicolour squid.
Another very interesting is the highly poisonous Portuguese Man of War whose tentacles can extend for 60ft.
Scientist Chris Bowler who spent three years aboard ship Tara will reveal the underwater beasts tonight at London's Science Museum.
Previously scientists thought there were fewer than 500,000 species of plankton but the expedition revealed 1.5 million.
The study also revealed the fragile state of the oceans.
It carried out the first ever sampling for plastic contamination in waters off the world's last pristine continent, Antarctica, and found thousands of plastic fragments per sq mile that can pose a threat to the environment.
"These fragments can cause serious damage to the ecosystem by releasing toxins into the food chain and being eaten by fish, sea mammals and sea birds that think that it is jellyfish," the paper quoted a Science Museum spokesman as saying.
"Because the southern ocean phytoplankton is so important for regulating the wellbeing of our planet by removing CO2 from the atmosphere and generating oxygen for us to breathe, this news from the Antarctic is particularly alarming.
"Every second breath humans take relies on microscopic plant life in the ocean," the spokesman added.
The research vessel Tara is currently in London's St. Katharine Docks.