Last night's Blue Planet looked at the vast expanses of open ocean described by David Attenborough as "the deserts of the sea" and by one cameraman as "liquid space".

The cameras followed a shoal of sardines, changing direction seemingly at random, as one, like a huge cloud of particles, a nebula of sardines. Suddenly they were under attack from giant marlin, living javelins. The twister of sardines knotted and unknotted, grouped and regrouped, taking shape like the special effects in The Mummy. Then along came a giant 14-metre Sei whale, its entire front half opening up, blossoming like huge variegated petals, engulfing hundreds of fish at once.

A manta ray, five-metres from wing to wing, cruised the ocean floor, inhaling clouds of plankton. I had always thought plankton were tiny shrimp and things, but the manta ray was feasting on fish eggs and sperm, pearl jam.

The finale was stunning - we followed a school of dolphin as they tracked a shoal of anchovies. Meanwhile, flocks of gulls were following the dolphins, knowing they would lead them to food. They attacked the anchovies simultaneously - the gulls diving to depths of 15 metres. Mammal, fish and bird, competing in the same element. A violent frenzy when viewed from above, yet balletic and beautiful underwater.