Last weekend, thousands of Grateful Dead obsessives from around the world hit the beach in Riviera Maya, Mexico, for “Playing in the Sand,” a four-day festival hosted by Dead & Company. Dead & Co. is the Grateful Dead revival band led by John Mayer and Bob Weir, and any show they play brings out Deadheads of all stripes—both new fans dipping their toes into the culture and veterans of the original band’s long, strange trip. And as we saw in November at their Madison Square Garden date, almost all the concert-goers embrace the rebellious hippie style that defines Dead tradition: tie-dye, Jerry Garcia iconography, and bootleg T-shirts emblazoned with custom Stealie skulls and dancing bears. We figured the Mexican shows would attract a particularly hardcore breed of Deadhead, so we sent fashion’s favorite roving photographer, Mordechai Rubinstein, a.k.a. Mister Mort, to shoot the attendees’ acid-soaked style all weekend. And the combination of the sandy beach, breezy vibes, and Mordechai’s singular eye brought out some of the most legendary Grateful Dead gear in the universe.

As Mordechai told us as he recovered from the four-day fiesta, “These were the truest and realest fans. Many were successful doctors and lawyers, but just as many seemed like regular folks who have been saving up for this trip. The best part was, everyone had a nice hotel room, but people slept on the beach! Even the rich guys slept on the beach. I’m talking 40, 50 people who wanted to hold their place in line for the shows. So it was very true to a Dead show. I couldn't believe all the different ages at the shows! There were families with three generations dancing in the sand. Out of hundreds of people I asked to take a photo of, only one person said no in four days. Everyone was super cool and inviting and down, and they brought their finest gear for this tour. Some even said, ‘I got dressed for you!’ I would’ve bought 100 tees and hats right off these guys, but you know what? None of them would have sold them. That’s how real these guys are. Every single person left saying, ‘I can’t wait for next year.’”

And what about Mayer’s on-stage fit—featuring vintage L.L. Bean and Off-White Nikes—which Mordechai got to photograph before the final show? “The vintage L.L. Bean anorak was the most genius thing to wear on the beach at night—it was genius. After the first few songs, he tied it around his waist. And the running shorts! I always say there’s a special caliber of musician who plays in shorts.”