Beaches along the Puerto Vallarta [1] coast are ephemeral things. During the June–September rainy season, waves, often stormy and rough, can wash sand out to sea, leaving clay and isolated rocks where your favorite beach used to be. But then, the calm, dry winter months arrive and the sand returns, transforming your favorite beach into to the warm, broad, golden strand that you remember.
Links:
[1] http://www.moon.com/destinations/puerto-vallarta/puerto-vallarta