Petacalco was a perfect a-frame barrel located in mainland Mexico. The wave was especially good because it was located at the mouth of the Rio Balsas, which was able to maintain the sand bars, focusing the waves. The sea floor drops off very deeply and quickly due to a deepwater canyon just off the beach at Petacalco.
Another unique aspect of the beach that makes the wave ride able when it was very big is that the curved beach faces south to southeast. This means that the prevailing onshore winds were side or offshore most days. All of these dynamics made a wave that was consistently big, hollow and perfect.
This wave was practically destroyed by development. Japanese financers funded the construction of the largest steel mill in a third world country in the town of Melchor Ocacampo. The large development of the mill was significant enough to change the name of the city to Lazaro Cardenas. This development resulted in a hydroelectric dam upstream of Petacalco on the Rio Balsas.
The dam impeded the necessary sand flow for maintenance of the sand bars severely. The final nail in the coffin was the harbor and its accompanying jetties located to the north of the break. The jetties allowed a large south swell in August of 1975 to strip the beach of so much sand that wave was ruined forever.
It still breaks occasionally when conditions are just right. However, the present wave is rare and does not compare to the perfect peaks that frequented the beach with surprising regularity before the dam and harbor. Most days it is now an a-frame shore pound without any shape.