i dont think so i think only unmanned subs can go down that far but even then im not sure if even those little robotic subs have gone all the way down to the bottom of the marianas trench (sp?) but yeah i forget if this was already mentioned and im not going to go back and read again lol, but i saw this monster hunters episode (i know, i know most their stuff looks like crap) but this one was actually pretty convincing and it was about sitings in the sea of cortez, about fishermen seeing these huge animals just under the surface that were way bigger than anything they had ever seen, and i mean fishermen who are on the ocean every day of their life no their sea critters so they would know if it was something normal, and one guy told story about how he was out in ocean driving full speed in his boat when all sudden they hit something and it stopped them dead like they had hit land, like it ripped his motor apart and everything from the impact and then they saw this huge thing swimming away, and another siting that was from a helicopter when they went on their little search that was shadow in the water that looked massive but it was gone by the time their boat in the water could get to it. im not saying i totally believe megalodon still exists im just saying there is obviously something out there and so you cant really totally write it off i mean we havent even discovered 50% of the life that is thought to exist in the ocean (we havent even discovered all the organisms on land in the jungles so def anything is possible in the depths of the ocean)