The immersive quality of 3-D is particularly well suited to undersea documentaries, and this one, directed by Howard Hall (Into the Deep), offers a close-up look at such fantastic creatures as the fried egg jellyfish, the mantis shrimp, the sand tiger shark, and the thuggish wolf eel. Johnny Depp and Kate Winslet trade off as narrators, delivering the requisite ecohomily near the end. G, 40 min.