Absolutely stunning. Simply the most beautiful underwater imagery I've ever seen. It's hard to remain not too affected when talking about ecology. Here, the off screen speech is quite subtle, not too naive and not boring, because sparingly used, which leaves long lapse of dreamy sequences, without a word. Technically, it's easily one of the best documentary ever made. The camera work and photography are incredible, the montage is very effective, alternating slow and fast paced sequences. The score is not too obtrusive. There is a very striking scene, which reminds me the nautical funerals of Laetitia in "Les Aventuriers" by Robert Enrico, if you see what I'm referring to, you will easily notice it, and I assure this scene will stick to your mind for days... Visually stunning, subtle, very recommended.
