Footage of giant trevally fish leaping out of the water to nom on young arctic terns was the first collective chill Blue Planet II sent down the nation's spines.

It's our green seas, not the blue, that bring life to our oceans. Here sunlight powers the growth of enchanted forests of kelp, mangroves and prairies of sea grass. They are the most abundant but fiercely competitive places in the ocean to live.

Camera technology has come forwards in leaps and bounds since the original Blue Planet aired in 2001, and this allowed Blue Planet II to show us never-before-seen spectacles of nature. One such technological advance was a camera able to film in absolute darkness, which allowed the team to capture a display like no other.

A standout part of Blue Planet II's incredible camerawork was the use of cameras attached to the animals. This technique was able to give the team an insight into life under the sea. Of course, first they had to boop the cameras onto the animals.

The deep sea is a weird, weird place, and not just because of the strange as hell fishies that live down there. In Blue Planet II we were taken down to see a natural feature that beggars belief -- an underwater lake. The lake itself is made of brine, which is heavier than regular water and so pools on the ocean floor.This was actually a re-visiting of a previous Blue Planet classic, but as well as the picture being of a much higher quality this time around, the Blue Planet II team got amazing footage illustrating how deadly these deep sea brine lakes are. Eels which delve into the lake are liable to toxic shock, and millions watched the eerie sight of the fish convulsing and tying itself in literal knots after diving into the brine.

The sea is a scary place, but no one was emotionally prepared for the Bobbit worm.Lurking in the seabed, the metre-long Bobbit worm (named after a woman who severed her husband's penis) hides in wait, and if a fishy comes to close it leaps out and seizes the fish in its jaws.

The Portuguese Man O'War is a curious thing. It looks like a jellyfish, but in fact it is a collective of organisms living together in a colony.Blue Planet II gave us an intimate look at how this oddity survives, and when I say intimate I mean intimate. We got an amazingly close-up look at how the Man O'War catches and digests its food, which it snares in its 40-metre-long tentacles before reeling in the unfortunate animal.This was another example of the superior technology in Blue Planet II coming to bear. Luckily there are no actual bears in the sea though. Can you imagine? In the sea? It doesn't bear thinking about.

Blue Planet II is a gold-standard in science programming, and they proved that time and time again, though perhaps never more so than when they managed to capture never-before documented behaviours. Chief among these: the mollusc master of disguise.

Attenborough documentaries are a consistent source of unbelievably tense chase sequences, remember the baby iguana and the snakes from Planet Earth II? Well Blue Planet II was no exception.We followed the gauntlet run by Sally lightfoot crabs at low tide, nimbly leaping from rock to rock trying to escape both moray eels and octopuses -- both of which are capable of leaving the water to pursue the heroic crustaceans.

Penguins are a staple for nature documentaries. You may think you've seen just about every scene involving a penguin, or even a swarm of penguins, that you could ever see.But have you seen penguins having to tiptoe past the huge mountains of blubber that are elephant seals? Just being in the vicinity of these behemoths puts the birds in significant danger, and so they hobble past, trying desperately not to step on anything remotely crunchy or squeaky.