I have all 4 DVDs (8 films) of the series; all are outstanding productions, and clearly the best of the marine documentaries I have seen (which is a lot).
Two aspects of the films stand out the most: the unbelievable image quality and visual narratives. The films capture aspects of animal behavior which have never before been seen on film (polar bears hunting beluga whales; orcas playing soccer with a baby seal, baitball feeding with marlin, dolphins and a sei whale; orca pods attacking a baby gray whale, and so on). And they capture this behavior with extremely moving beauty.
Unlike many nature documentaries, there are no talking heads, only background narration. You get a non-stop flow of images creatively matched to orginal music. But for those who do enjoy the talking heads, each film has great bonus tracks with interviews of the camerafolk, producers, scientists, etc.