James Cameron wants you to believe. He wants you to believe that aliens are killing machines, humanity can defeat times travel i  cyborgs, and a film can transport you to a significant historical disaster. In many ways, the planet of Pandora in "Avatar" has become his most ambitious manner of sharing this belief in the power of cinema. Can you leave everything in your life behind and experience a film in a way that's become increasingly difficult in an era of so much distraction? As technology has advanced, Cameron has pushed the limits of his power of belief even further, playing with 3D, High Frame Rate, and other toys that weren't available when he started his career. But one of the many things that is so fascinating about "Avatar: The Way of Water" is how that belief manifests itself in themes he's explored so often before. This wildly entertaining film isn't a retread of "Avatar," but a film in which fans can pick out thematic and even visual elements of "Titanic," "Aliens," "The Abyss," and "The Terminator" films. It's as if Cameron has moved to Pandora forever and brought everything he cares about. (He's also clearly never leaving.) Cameron invites viewers into this fully realized world with so many striking images and phenomenally rendered action scenes that everything else fades away. The first Avatar was a pioneering 3D sci-fi spectacular which Cameron delivered in 2009. Now, after 13 years of unimaginably expensive pixel-crunching, the aquatic followup has arrived, with a third and a fourth on the way. This one is available in 3D and 2D, and so at any rate keeping loyal to that three-dimensional vision that Cameron almost single-handedly revived but which the rest of the industry has quietly forgotten about. Yet the whole idea of the “avatar” from the first movie – the artificially created body that can be remotely piloted into an unknown world and which crucially formed a dramatic part of the audience’s 3D experience – has been left behind. The effects now, technically impressive as they are, amount to high frame-rate motion smoothness which is soulless and inert, creating not so much an uncanny valley but an uncanny Mariana Trench down in the depths. Cameron’s undersea world is like a trillion-dollar screensaver. Where is the oceanic passion and jeopardy of great Cameron movies such as Titanic or The Abyss? The situation is that ex-human Jake Sully (Sam Worthington) is committed to the Na’vi body he assumed when insinuating himself among the blue-bodied, pointy-eared tribe as part of the “avatar” strategy in the first film, before falling in love with dynamic warrior Neytiri (Zoe Saldaña) and siding with her people against the humans who would exploit the Na’vi’s mineral resources. Now, some years later, Sully and Neytiri are living happily with their children and their stepdaughter Kiri – whose connection with the original film soon becomes apparent – and also a semi-feral human kid called Spider. But just when they thought they were happy, the “sky people” of planet Earth reappear and there is an admittedly ingenious twist concerning the gung-ho marine colonel Miles Quaritch, memorably played by Stephen Lang. Sully’s family have to leave their rainforest habitat and hide away among the far-off Metkayina, an amphibious reef people led by Ronal (Kate Winslet) and Tonowari (Cliff Curtis). There they must learn the mystical Metkayina art of existing for long periods underwater. Sully’s children and Tonowari’s children, at first spiky and rivalrous, become as close as cousins. But this new Eden can’t last forever either.