You would have to dive to cut the cable. Easier, if your boat is powerful enough, to pull until the cable breaks. Ignoring malicious activity, could be something as simple as an anchor got caught and they pulled the station with it?

Or, you can use the USS Jimmy Carter submarines cable splicing room to do whatever you may want to do...

The only people downvoting this are spooks or people who dont know what im talking about.

It cost 300k, but I can't imagine there's a huge blackmarket for fencing sea-water salinity monitors and the like, so I doubt stealing it would be worth anyones trouble.