Forskare har filmat fiskar på 7,7 km djup;"experts claim it is the deepest living fish species ever discovered":
http://www.practicalfishkeeping.co.uk/pfk/pages/item.php?news=1841
http://news.bbc.co.uk/2/hi/science/nature/7655358.stm
<<<(^:>*
The water is also exceptionally cold - nearly freezing - and the water pressure is "8,000 tonnes per square metre, equivalent to that of 1600 elephants standing on the roof of a Mini car."