when you've finished Planet Earth be sure to move on to Blue Planet/Blue Planet II (currently showing over here on BBC).
This takes you on and under the sea to depths rarely explored. This highlights the lack of imagination of the Sci Fi creators. When they invent aliens they always seem to have two arms, legs, eyes and ears etc just like us yet there is a vast array of true aliens living on this planet with us.
Also amazes me how creatures in such a dark environment are always the ones with the most vivid colouring.