Watching thick fog settle over the Azov Sea, a Ukrainian soldier in the port city of Mariupol worries the weather will make it harder to observe “the enemy”.
His unit is on high alert after a confrontation between Ukrainian and Russian ships this weekend in the Kerch Strait — a narrow strip that links the Azov and Black seas.
“Whenever we get the order we are ready to repel an attack and defend our positions,” the 26-year-old tells AFP, giving his nickname Kit, or “whale” in Ukrainian.
“The border guards that patrol the sea are the first line of defence. If their positions are destroyed, we will take the hit,” he says.
On Sunday, Russia fired on and seized three Ukrainian ships. Kiev and its Western allies are demanding that Moscow release the vessels and their sailors.
“Our ships were advancing peacefully towards Mariupol and they were attacked,” Mr Kit said. “We were all put on alert.”
If the long-running conflict between Ukraine and Russia were to intensify, Mariupol would likely find itself on the frontline.
The industrial city has already known war, having been briefly occupied by pro-Russia rebels at the start of the conflict in 2014, a strategic asset in a tussle between Moscow-backed forces and Kiev.
It was recaptured by government forces after a few days and remains the only major city in southeastern Ukraine under Kiev’s control.
In 2015, 31 people were killed by shelling in Mariupol and 100 others were wounded.
Today, the port city is only around 10 kilometres (six miles) from the frontline that separates government-controlled territory from Moscow-backed rebel republics.
In Chervone, a village just south of Mariupol, around 60 people dig trenches in what they say is a bid to protect the city from a Russian advance.
They are all members of a volunteer centre that helps children in need. Even the children have been mobilised, helping adults to dig new pits.
“A few hundred meters from here are our children, our families, a centre to help refugees,” says Gennady Mokhenko, a Pentecostal pastor who founded the centre.
“In case of a Russian attack from sea, these trenches will turn into a frontline in just a few minutes,” the 50-year-old says, adding that he is ready to fight for Ukraine.
“I hope this will never happen,” says the pastor, wearing a metal crucifix on his chest and camouflage.
One of the centre’s former students, 22-year-old Bohdan Petlitsky, says he is also ready to give up his job as a firefighter to join the army.
“If there is an attack, I will be ready to take up a weapon to defend Ukraine and Mariupol,” he says.
Not everyone is as fearful.
Mykola, a 52-year-old who was working out on a sports field on the banks of the Azov Sea, said: “Even if Russian paratroopers land here, it doesn’t mean it will be something bad. We are all brothers.”
Right now, he says, “I don’t think anything serious will happen.”