At the aft, a gunner tightly grips the handle of a heavy machine gun from behind, carefully scanning the horizon for any danger.
One hour in coastal patrol, about 5 nautical miles off the Ukrainian coast, a broken radio message cuts through a dull drone of diesel engines and a lightly armed vessel suddenly arrives.
“Boat 23, this is Boat 444,” is a harsh Russian voice in the airwaves.
“We are reminding you to keep a safe distance,” the operator warns.
Ahead, a Russian coastal security ship moves over the horizon, a floating steel gatekeeper beyond the naval force rising at sea.
The message is clear: do not go further.
“If we don’t turn around, there will be trouble,” says Cmdr. Nikolay Levitsky of the Ukrainian Marine Guard.
The Russian Ministry of Defense makes no secret as to what may be involved in that trouble. In its muscle-flexing show of naval power in one of the world’s smallest seas, it has released dramatic images of ships launching barrage of missile shattering in waves.
The Kremlin insisted that this was just a naval drill, a practice that would not pose a threat to anyone. This landlock speaks of the achievement of a flotilla of 15 ships going from the Caspian Sea to the Black Sea basin with 13 ponds from a 60-mile (100 km) canal.
But Ukrainian military officials, just a few miles away, are watching the buildup with concern.
“In the past two weeks, it has become more dangerous because the Russian Federation has sent several landing ships from the Baltic Sea and the North Sea,” says Captain Roman Goncharenko of the Ukrainian Navy in Mariupol.
“Officially this is the practice. But those ships are still in the area, and in our eyes it can be dangerous,” he told CNN from the deck of Soviet-era Donbass, a war search and rescue ship, called 1969 It was built and docked in the port city.
Buildup on land and sea
Tens of thousands of Russian soldiers, backed by armored columns, were headed to eastern Ukraine, where Russian-backed rebels are fighting a peace separatist war with government forces in which thousands of people have been killed.
US Pentagon spokesman John Kirby said on Monday that there were “still quite a few” Russian forces along the border with Ukraine and in Crimea.
Ukraine claims it now violates international law by restricting Azov’s access to the Sea, which Russia and Ukraine agreed to share in the 2003 agreement.
Ukrainian authorities say that commercial shipping along an important route to the east faces additional checks and delays, but Russia says traffic is not banned.
This is not the first time Russia has increased its naval power towards Ukraine. In 2018, the Russian Coast Guard attacked a Ukrainian tugboat in the area. Russian ships fired on Ukrainian naval ships, seized three and detained 24 sailors. Both sides accused the other of violating the rules of the sea.
Tension is also visible on the ground in the early hours of the sea of Azov. In Mariupol, a dozen Ukrainian marines dressed in battle clothes and balaclaves, maneuvers, patrolling the harbor with their rifles at the ready, which they say, drill anti-sabotage.
Ukrainian naval officials say they have no choice but to plan a possible Russian attack and more ground forces should be deployed in the event of an attack.
They already called Russian action on the Sea of Azov the “creep business” of the region.
“Russian ships behave increasingly aggressively, entering prohibited areas or in places where they should have sought permission from Ukrainian authorities,” says the patrol boat commander, Levitsky.
After warning the Ukrainian coast guard vessel to be too near by the Russian ship, CNN asked him what would happen if we did not return. Hellsman shouted, “It would be very dangerous.”
Levitsky looked at him contemptuously and blasphemously, saying, “This can’t be good.”
Zahn Ullah of CNN contributed to this story.