Hidden beach or "Playa Escondida" as it's known in the local tongue is a beautiful beach within a cave at one of the Marieta Islands north west of Puerto Vallarta.
The beach is visible from the sky but not from sea, your guide will point you to the small 'tunnel' when you get close and you'll swim your way into the secret wonderland. Once inside there's a white sandy beach, the same crystal blue waters as the bay you came from and a sense of calm as you wander around Playa Escondida!
The hidden beach is accessible by sea only so you're best to book a boat tour to get there. A number of tour boat companies work in the area, take a look online or head to the Marina Vallarta and take your pick from the different tour operators. There's a range of offerings at different prices with different inclusions so work out which is best for you.