Cables underwater fuel more than 95 percent of daily communications around the world. Some governments have radar tracking systems to monitor areas around their cables, the US is one of them. The US is worried about Russia and the potential that they may sever these wires. What would this do to us though? Well, internet would be down...for a while. And an action like this by Russia would most likely cause quite a lot of tension. Cables get cut all the time on accident by natural disasters and anchors. It is possible for a person to cut a cable without the use of high tech equipment. A pair of garden shears and some scuba equipment will do. But thousands of volts could kill you before you get to reap any sort of benefit from your plan. Should we be worried about Russia potentially taking us off the grid for a few hours? I don't think so. Plus, this would just be another provocation point from Russia to the US. 

Ellen Kent

http://www.reuters.com/article/2015/10/26/us-usa-security-russia-idUSKCN0SK02G20151026