>> 400 feet. >> reporter: eventually descending 400, 500, more than 600 feet beneath the surface of the sea. they have trained to move the submarine as carefully and as quickly as possible. >> 13 degree up angle. >> reporter: soon, we are all leaning with no effort. it is precision work in these waters of the eastern mediterranean. they have to be ready. there are others here, too. >> we've put this submarine right in this eastern portion of the mediterranean to counterbalance the russia buildup in syria. >> reporter: do you have company here in the mediterranean? >> we do have plenty of company. the russians are very active and we're active with them. >> passing 2-7-0 to the left. >> reporter: the u.s. aware the russians are trying to send a message. the russians have demonstrated their willingness to use missiles from submarines. they did it from the black sea. >> yes. >> reporter: -- into syria, and now the russians are here in the mediterranean? >> they absolutely are, and we're watching them very, very closely. >> reporter: you are. >> yeah. there's really not a day where we're not watching them every single day. >> reporter: are they watching us?