SINGAPORE – Just as aspiring astronauts yearn to go to outer space to walk the craters of the moon, film-maker James Cameron had dreamt, since he was a boy, of traversing territory that even fewer have set foot on – the depths of the ocean floor. 

In 2012, piloting a submersible that he helped to design and engineer, Mr Cameron ventured into the frigid, oceanic valleys of the Mariana Trench, reaching its deepest point – Challenger Deep – at more than 11km from the water’s surface, where sunlight does not penetrate, and the water pressure is bone-crushing.