Beachgoers had their day on the sand ruined when the Russian navy arrived and took over the area.
A number of amphibious armoured personnel carriers suddenly rolled on to the beach interrupting the tranquility of the Caspian Sea.
Footage from the city of Kaspiysk shows the stunned daytrippers suddenly in the middle of a naval exercise.
And even children who had been splashing about in the surf, were ordered out of the sea.
The forces were rehearsing for one of seven major shows of strength across Russia on Sunday marking Navy Day, with many naval vessels visible out at sea.
Some 30 ships, support vessels and amphibious personnel carriers like the 8×8 wheeled BTR-80 will take part in the display at Kaspiysk.
Protesters hit out at the arrival of the armoured carriers as families were on the beach at the time.
A woman said: “The water is already contaminated.
“The military show would only worsen the pollution.
“Russia can only show its power and doesn’t care about people and the planet,” she said.
Another mother argued that the children were “delighted” at seeing the navy vehicles and the sailors.
She added: “Parents had been warned in advance to take their children out of the sea.”
And mother Sonya Pashaeva who filmed the spectacle said seeing the amphibious armoured carriers go into the sea was “amazing”.
The city of Kaspiysk has a 102,000 population and is Russia’s main naval base on the Caspian Sea.