A Russian destroyer and a US Navy guided-missile cruiser sailed dangerously close to one another in the Philippine Sea on Friday.

Videos of what the US Navy described as an "unsafe and unprofessional" encounter appear to show Russian sailors sunbathing on the helicopter pad.

Their presence could be seen as a taunt, though neither the Navy nor the Department of Defense would speculate about exactly what the sailors were doing.

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A Russian destroyer and a US Navy guided-missile cruiser nearly collided at sea on Friday. Videos released by the Navy appear to show Russian sailors sunbathing shirtless on the back of their warship during the close encounter.

Read more: Shocking photos show Russian destroyer playing a dangerous game of chicken with a US warship

In a statement accompanied by photos and videos of the incident, the US 7th Fleet accused the Russian destroyer DD572, which Russia identified as the Admiral Vinogradov, of engaging in "unsafe and unprofessional" behavior by sailing dangerously close to the USS Chancellorsville, a Ticonderoga-class cruiser.

The Russians accused the American vessel of acting improperly, arguing that the Chancellorsville abruptly changed course and cut across the path of the destroyer.

Read more: US Navy videos show just how close a Russian destroyer came to colliding with a US warship

Amid the back-and-forth over who is to blame for the latest US-Russia confrontation, eagle-eyed observers took note of something peculiar in the videos released by the Navy — what appears to be Russian sailors sunbathing shirtless, if not naked, as one appears to be, on the helicopter pad.

—Mike Yeo 杨启铭 (@TheBaseLeg) June 7, 2019

NPR reported the unusual Russian behavior in an article discussing the showdown between the Russian and US warships.

"In an odd sight," the writer observed, "the videos show several Russian service members seemed to be sunbathing on an aft platform aboard the destroyer as it nears the American warship."

The video is a little blurry, so it is difficult to say for sure.

While Department of Defense and Navy officials noted Russia's behavior, none were willing to speculate on the record about what exactly the Russians were doing or why.

The US has decided to lodge a formal diplomatic protest in response to this "unsafe" naval encounter, Acting Secretary of Defense Patrick Shanahan said Friday, adding that Russia's actions "will not deter us from conducting our operations."