Zac Efron sports retro beach wear on Tybee Island

FILE - SEPTEMBER 17: Actor Zac Efron completed a stay in rehab five months ago. CANNES, FRANCE - MAY 24: Actor Zac Efron attends the "The Paperboy" photocall during the 65th Annual Cannes Film Festival at Palais des Festivals on May 24, 2012 in Cannes, France. (Photo by Pascal Le Segretain/Getty Images) Getty Images

Credit: Jennifer Brett

Credit: Jennifer Brett

FILE - SEPTEMBER 17: Actor Zac Efron completed a stay in rehab five months ago. CANNES, FRANCE - MAY 24: Actor Zac Efron attends the "The Paperboy" photocall during the 65th Annual Cannes Film Festival at Palais des Festivals on May 24, 2012 in Cannes, France. (Photo by Pascal Le Segretain/Getty Images) Getty Images

Zac Efron and Robert De Niro have gone coastal.

Their movie "Dirty Grandpa" first filmed in metro Atlanta earlier this year before heading eastbound and down. They've been filming at Tybee Island.

The movie is about a guy (Zac) who takes his lewd gramps (Bob) on a spring break trip to Florida (Tybee).

Apparently the plot involves time travel back to about 1988. Check out these neon britches and Flashdancey crop top!