The former "One Direction" singer couldn't look more relaxed Friday while enjoying a shower right next to the beach in the Tuscany town of Porto Ercole. That name, btw, means Port Hercules -- appropriate for Harry's physique.

He was flaunting his heavily inked bod, too! He's got about 60 tattoos ... which he had to cover for his first starring role in the film "Don't Worry Darling."

He definitely earned some R&R after wrapping his movie "My Policeman" in Venice earlier this week. The Amazon project had him filming all over England ... including in London, where he donned an old school London police uniform.

He's the lead in a film that's an adaption of the 2012 novel by Bethan Roberts.

Harry plays a policeman named Tom, who is involved in a love triangle between school teacher Marion (played by "The Crown" star Emma Corrin) and a museum curator Patrick (played by English actor David Dawson).

The novel's set in the 1950s when homophobia was rampant ... forcing Tom to marry Marion, who then secretly shares him with Patrick. The plan eventually falls apart.