>> i want to bring in now eric. he's at the university of new south wales wales. at these depths, what is the ocean really like? >> well, it is pitch black. it is because ocean water doesn't let light through. if you go slightly below the surface, sure there's still a little bit of light. but as anybody who's been diving knows, the further down you go, the less the light goes through. as soon as you get like 300 feet or so below the surface, nothing gets there there. this is darkness only. >> they said that silt and sediment would be a problem. can you explain the ocean ooze or the sediment to me and to the audience. if the plane is retsing down there, what is the sea floor like? >> so, the sea floor down there is a few feet, maybe 30 feet of what we call marine snow.