At a time when the eight NATO nations bordering the Baltic Sea are on high alert after a string of undersea power and internet cables were suspiciously severed, Russia's shadow fleet is getting extra attention.

NATO is ratcheting up its guard against suspected attempts to sabotage underwater energy and data cables and pipelines that crisscross the Baltic Sea.

Under steel grey skies, the Dutch minehunting vessel Schiedam cuts through the waters dividing Denmark and Sweden, part of NATO's Baltic Sentry mission to protect underwater infrastructure in the Baltic Sea.

To try to deter any future saboteurs, Estonia has since deployed three vessels near the remaining Estlink 1 cable in the busy Gulf of Finland, an arm of the Baltic Sea that at its eastern end stretches into Russian waters. Moscow has denied any involvement in the cable breaches.

The European Union and NATO must strengthen cooperation to protect critical energy infrastructure from attacks, which pose a growing threat to European stability. The Kremlin, with its history of weaponizing energy,

Northern Europe’s Baltic Sea is bordered by nations including Germany, Russia and Latvia. Many critical cables and pipelines cross the seafloor. But with tensions rising in the region, NATO is looking for ways to ensure all that infrastructure stays safe.