That train-time again (Due to public outcry I have updated this bag of coal with some more coal...)

Nah man. Seabed seismic exploration is the name of the game.

We get on a boat, about 45 men and women (I work in what's called 2D seismic, small ship, small crew), deploy an eleven kilometer long cable into the water which consists of mostly hydrophones and electronics. Then we deploy six "guns" (compressed air sources) which set of a pressure wave through the water at intervals. The hydrophones then pick up the return "echo" of the pressure waves as it's reflected back up from geological formations deep below the seabed itself.
So we travel up and down pre-plotted lines like that for six weeks and then we go into port, change crew and we go home. Easy.
Well, not always... Besides ourselves we also control up to five chase vessels that assist us, smaller boats that we use to keep our track clear of commercial vessels, fishing boats, fishing gear, debris, etc. When working in waters where most bridge personnel speak english and there's little fishing activity it's not too much of a worry, but getting into parts of the world, where fishermen don't speak english, commercial vessels don't answer the radio, with a lot of fixed fishing gear, and with very slow chase boats it gets..... Interesting.
Dragging that 6 million dollar 11 kilometer cable through all that without snagging it in anything is stressinducing to say the least.
And again, we're only a 2D ship, only one cable. The biggest 3D ships tow up to 28 streamers....
But it's actually not the cost of replacing the streamer if it's damaged that's the real killer, it's the wait for new parts. Loss of revenue for our small ship ranges between $ 70.000-130.000 a day we're not working, the big ships between $1-2.000.000.... Under those conditions you really, really, really, really, REALLY do not want that cable tangled or damaged in any way.
And when you do a good job of keeping it clear you might still lose it to sharkbites, or misjudged weather condition. Happened to me a while back, a frakking shark bite took half our streamer off. It's fun trying to retrieve that again in the high seas at night....