At the stern, a rifleman grasps the handles of a single heavy machine gun bolted to the rear and carefully scans the horizon for threats.
One hour after the start of the coastal patrol, in rough seas, about 5 nautical miles off the Ukrainian coast, a crackling radio message cuts through the dull drone of the diesel engines, and the lightly armed ship suddenly takes off.
“Boat 23, that’s boat 444,” says a stern Russian voice over the waves in the air.
“We remind you to keep a safe distance,” warns the operator.
In front of us, a Russian coastal defense ship appears on the horizon, a floating steel goalkeeper of the growing naval forces that are gathering in the seas beyond.
The message is clear: don’t go any further.
“If we don’t turn around, there will be trouble,” says Cmdr. Nikolay Levitskiy from the Ukrainian Navy Guard.
The Russian Defense Ministry makes no secret of what these difficulties could bring. In its muscle-flexing demonstration of sea strength in one of the smallest seas in the world, it has posted dramatic images of ships firing rocket shots that screech above the waves.
The Kremlin insists this is just a naval exercise, an exercise that poses no threat to anyone. It is about the achievement of a flotilla of 15 ships that sail from the Inland Caspian Sea over a 100 km long canal with 13 locks to the Black Sea basin.
But Ukrainian military officials, just a few miles away, are watching the build-up with concern.
“It has become more dangerous in the last two weeks because the Russian Federation has sent several landing ships from the Baltic and North Seas,” says Captain Roman Goncharenko of the Ukrainian Navy in Mariupol.
“Officially, they’re drills. But these ships are still around here, and our vision is that it can be dangerous,” he told CNN of the deck of the Soviet-era Donbas, a rusty search and rescue ship that was built and docked in 1969 was in the port city.
Construction on land and at sea
The build-up of the navy follows international alarms about a recent surge in Russian land forces near the border with Ukraine and in Crimea, which was annexed by Russia in 2014.
Tens of thousands of Russian troops, supported by tank columns, were spotted en route to eastern Ukraine, where Russian-backed rebels waged a bitter separatist war with government forces in which thousands died.
Ukrainian President Volodymyr Zelensky granted CNN unprecedented access last month when he went to frontline positions to support his frontline troops. The Kremlin also said the troop movements were “military exercises” and finally announced a withdrawal of forces late last month, although US officials say it is unclear how many Russian troops have been withdrawn.
US Pentagon spokesman John Kirby said Monday that there were “still some” Russian forces along the border with Ukraine and in Crimea.
US Secretary of State Antony Blinken will be in Kiev this week to meet his Ukrainian counterpart and Zelensky. The State Department says it intends to “reaffirm” US support for Ukraine “in the face of ongoing Russian aggression.”
Ukraine claims the aggression is now in violation of international law by restricting access to the Sea of Azov, which Russia and Ukraine agreed in a 2003 agreement.
Ukrainian officials say merchant shipping is facing additional controls and delays along a key route east, but Russia insists that traffic is not banned.
This is not the first time Russia has exercised sea power over Ukraine. In 2018, the Russian Coast Guard rammed a Ukrainian tug in the area. Russian ships fired at Ukrainian naval vessels, seizing three and detaining 24 seamen. Both sides accused the other of violating maritime laws.
American ships were also challenged. At the beginning of this year, a low pass of a Russian fighter aircraft in the Black Sea was observed from the deck of the US destroyer USS Donald Cook.
The tension on the troubled waters of the Azov Sea is also visible on land. In Mariupol, a dozen Ukrainian marines in combat suits and balaclavas are practicing maneuvers, patrolling the port with rifles on hand and allegedly carrying out sabotage exercises.
Ukrainian naval officials say they have no choice but to plan a possible Russian attack and that if there is an attack, more ground forces will be on standby to deploy.
You already call the Russian action on the Sea of Azov a “creeping occupation” of the region.
“Russian ships are becoming increasingly aggressive and entering prohibited areas or places where they should have permission from the Ukrainian authorities,” says Levitskiy, the patrol boat commander.
After the Russian ship warned the Ukrainian coast guard ship not to get too close, CNN asked him what would happen if we didn’t return. The helmsman shouted: “It would be very dangerous.”
Levitskiy looked at him disapprovingly and reluctantly and just said, “It can’t be good.”
CNN’s Zahra Ullah contributed to this story.