>> you see species down there you don't see anywhere else. >> all sorts of life forms, you don't see underwater rivers -- >> what is an underwater river. >> it is density, water moves because it is dense, if it is salty or cold, the water is actually water that cuts across the sea bed. >> of water that is more dense? >> yeah, it floats, it started to use the antarctic and pours into the basins, where it comes up against a steep cliff, it makes a waterfall. the lakes are even more amazing that you can go to the bottom of the ocean and see what looks like a lake at night. >> would it interfere with the towed pinger locators? >> potentially it could, it makes a little bit of extra noise, there are some that are in that frequency range. there is the physical movement of the propeller and pieces on it that can interfere. it should be distinguishable, but as the battery gets weaker and weaker, they want it as quiet as possible down there. >> the side sonar scanner, i think it is called bluefin, how deep with it go? -- deep can it go? >> 4,500 meters is the operating maximum. we're right about there.