>> 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, the lakings are own 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 -- >> the side sonar scanner, i think it is called bluefin, how deep with it go? >> 4500 meters it can go. that is operating maximum.