The creatures include the world’s longest animal - a siphonophore which can extend for up to 150ft, bristling with poisonous tentacles.

It is made up of countless tiny creatures, each with a specific function such as swimming, eating, floating or reproduction, linked together by a long hollow tube similar to an umbilical cord.

Other creatures include what look like brightly coloured sea centipedes, ghostly fish and technicolour squid.

The underwater beasts will be revealed tonight at London’s Science Museum by scientist Chris Bowler who spent three years aboard the French research ship Tara.

It found one million new species, mainly plankton, as it crossed the Atlantic, Pacific, Southern and Indian oceans on a 70,000 mile journey.

Previously scientists thought there were fewer than 500,000 species of plankton but the expedition revealed 1.5 million.