I think perhaps I found the beach I searched for long & hard in Cuba only to come up empty handed. It’s in Palomino, Colombia. It’s on the Caribbean in the middle of nowhere beneath the Sierra Nevada de Santa Marta mountains, the highest coastal mountain range in the world. It’s beaches are white sand, wide & gorgeous. It’s super chill. There’s no one here. No resorts of any kind. The town consists of a few dirt roads barely big enough for scooters. The surf is a bit aggressive & would rightfully scare off some folks, as do the red “swim at your own risk” flags posted everywhere (it was yellow one day), but I actually kinda prefer to get knocked around a little bit as it keeps things interesting. Those visiting on the weekend included quite a few locals as well as foreign travelers. You’ve got the hippies w their packs & guitars camping of course, you’ve got hostels whose spot on the beach in front of “the center” is the happening spot if there is one, & the relatively higher priced huts & bungalows further down the beach. It’s so quiet everywhere in a really good way. Palomino is flanked by 2 rivers, one of which you can rent inner tubes & tube down, although you don’t cover much ground as the current is nearly non-existent. So I got a lot of R&R, posted a lot of blogs & rested up for the trek North to alta Guajira. 
I of course can’t take credit for Palomino. My arduous research revealed Taganga, 2+hrs W of here, could be a good spot but the more I read, the more I found it USED to be a good quiet spot but now hordes of tourists have overrun the small fishing village. I came across Palomino for an untouched beach in an online Rough Guide article listing the top 10 places in South America you’ve never heard of. Umm. It’s like it was written for me. As for the rest of the places on that list? I’d actually heard of several others, but you can bet your ass I’m keeping many of them in mind.