Repair? This thread is about interception. You don't want to damage the cable, because a) it draws attention to your activities and b) if you've broken the cable, it is no longer carrying the information you seek to intercept.Perhaps - but on shore they are more easily repaired, and your chances of getting away with it are low. I hope that somebody has paid attention to protecting key points.
Undersea cables are difficult and expensive to repair, and ships passing in international waters can be totally innocent looking, but be equipped with ROVs, divers, and so on.
Destroying cables is the modern equivalent of bombing the shit out of Dresden or Coventry. Today there are MUCH more effective ways of conducting operations against the enemy's telecommunications, and indeed that do not provoke actual war. Indeed, prevent it, in some/many cases.
Why is why there is no point in expanding this thread to cover all the other infrastructure in the sea. Not much point in intercepting a power cable, if it carries any intelligence at all, it will only be telemetry data. If you want to disrupt the enemy, then destroying it probably is your best bet. But that warrants its own thread.