<P> In May 2017 an unidentified type of snailfish was filmed at a depth of 8,178 metres (26,800 ft). </P> <P> In 2016, a research expedition looked at the chemical makeup of crustacean scavengers collected from a range of 7,841--10,250 metres within the trench . Within these organisms, the researchers found extremely elevated concentrations of PCBs, a chemical toxin banned for its environmental harm in the 1970s, concentrated at all depths within the sediment of the trench . </P> <P> Like other oceanic trenches, the Mariana Trench has been proposed as a site for nuclear waste disposal, in the hope that tectonic plate subduction occurring at the site might eventually push the nuclear waste deep into the Earth's mantle, the second layer of the Earth . However, ocean dumping of nuclear waste is prohibited by international law . Furthermore, plate subduction zones are associated with very large megathrust earthquakes, the effects of which are unpredictable for the safety of long - term disposal of nuclear wastes within the hadopelagic ecosystem . </P>

Who went to the bottom of the marianas trench