This obviously wasn't made on the same huge budget as Attenborough's series and, as such, lacks the majestic set piece shots that make those series so amazing.
This is much more about the issues affecting the oceans than getting great pictures.
It has its share of great shots, there's something about the underwater realm that ensures that is the case, but it's also true (at least in the form it was shown on TV, I've not seen the DVD version) that there are some rather dull interludes.
It also seems slightly amazing that Cousteau Jr has done so little diving around the world, but I have to assume his remarks weren't for some affect.
Is this is a good as Blue Planet? No, but it's not aiming for the same target and, if you can (unlike some of the other reviewers) stop tutting and sighing and switching off 10 minutes in because it isn't BP2 then you'll probably learn more than you will from Blue Planet (or many of the 'landmark' nature series).
Not a must have or must see, but a useful intro (mostly) to different aspects of the oceans of the world and certainly not as awful as those 1 star reviews suggest.