The oceanic trenches are hemispheric-scale long but narrow topographic depressions of the sea floor. They are also the deepest parts of the ocean floor.

Trenches define one of the most important natural boundaries on the Earth’s solid surface: the one between two lithospheric plates. There are three types of lithospheric plate boundaries: divergent (where lithosphere and oceanic crust is created at mid-ocean ridges), convergent (where one lithospheric plate sinks beneath another and returns to the mantle), and transform (where two lithospheric plates slide past each other).

Trenches are a distinctive morphological feature of plate boundaries. Along convergent plate boundaries, plates move together at rates that vary from a few mm to over ten cm per year. A trench marks the position at which the flexed, subducting slab begins to descend beneath another lithospheric slab. Trenches are generally parallel to a volcanic island arc, and about 200 km (120 mi) from a volcanic arc. Oceanic trenches typically extend 3 to 4 km (1.9 to 2.5 mi) below the level of the surrounding oceanic floor. The greatest ocean depth to be sounded is in the Challenger Deep of the Mariana Trench, at a depth of 10,911 m (35,797 ft) below sea level. Oceanic lithosphere moves into trenches at a global rate of about a tenth of a square metre per second.

James Francis Cameron (born August 16, 1954) is a Canadian film director, film producer, deep-sea explorer, screenwriter, visual artist and editor. His writing and directing work includes Piranha II: The Spawning (1981), The Terminator (1984), Aliens (1986), The Abyss (1989), Terminator 2: Judgment Day (1991), True Lies (1994), Titanic (1997), Dark Angel (2000–02), and Avatar (2009). In the time between making Titanic and Avatar, Cameron spent several years creating many documentary films (specifically underwater documentaries) and co-developed the digital 3D Fusion Camera System. Described by a biographer as part-scientist and part-artist, Cameron has also contributed to underwater filming and remote vehicle technologies. On March 26, 2012, Cameron reached the bottom of the Mariana Trench, the deepest part of the ocean, in the Deepsea Challenger submersible.

He has been nominated for six Academy Awards overall and won three for Titanic. In total, Cameron's directorial efforts have grossed approximately US$2 billion in North America and US$6 billion worldwide. Without adjusting for inflation, Cameron's Titanic and Avatar are the two highest-grossing films of all time at $2.16 billion and $2.78 billion respectively. In March 2011 he was named Hollywood's top earner by Vanity Fair, with estimated 2010 earnings of $257 million.