Russian ships ‘plotting sabotage in the North Sea’ [1]
[0] https://www.independent.co.uk/news/uk/home-news/uk-undersea-...
[1] https://www.independent.co.uk/news/world/europe/russia-ships...
That said, there is a limited amount that can be done in international waters without creating an international incident. Law Of The Seas, Freedom Of Navigation, etc.. It is to our advantage for example, when we want to prevent CCP's from denying access to international waters around Taiwan or Phillipines, but to Russia's advantage when scouting undersea cables in international waters.
They can field more "research" vessels than we'd typically field mil vessels, but I'd bet real money that that ratio just changed a lot in the past few weeks, as it hits the press.
Back during the cold war, there was very often a Soviet "fishing boat" trailing after any substantial US Navy fleet. Said fishing boat may have had far more antennas than any fisherman would expect, but far less interest in catching fish.
Fast forward - what would be the cost of having cheap western drones hanging around nearby, when suspected Russian assets were close to undersea cables, pipelines, and such?
That said, satellite tracking shipping is pretty easy - It's interdicting ina timely fashion which is not.
But cheap drones can transmit "don't do that!" warnings. And also video footage of the situation. Which would seriously change both the maritime law and political situations.
If the suspicion is high enough, it's pretty standard for a US submarine or surface group to shadow whatever it is. It's free practice for the submarine crew.
This happened when the Russian ships visited cuba earlier this year.