It is a natural reserve consisting of a cluster of granite islands poking out of the sea. The three largest are known as Roca de Los Arcos (Arch Rock), Roca de la Tortuga (Turtle Rock) and Roca del Diablo (Devil Rock). The name of the latter is from a figure that forms on the cliff on one side.

The largest rock is 160 m wide by 250 m long and 54 m high. 

These rocky islands can be seen from downtown Puerto Vallarta, but to appreciate their size and stunning beauty, you need to get up close to them. 

Along with arches, in Los Arcos National Marine Park you’ll find caves, deep tunnels, and a coral reef. It seems that the waters in the National Park are the deepest, ranging from 9 to 480 m (30-1,600 ft.), it is quite an adventure to explore the archs.

The warm blue waters are home to a number of tropical fish and other sea creatures. These include eels, rays, trumpetfish, and even sea turtles. This is one of the best places in all of Banderas Bay for swimming, diving and snorkeling.

Additionally, the park is well known for its vast biodiversity. These huge rocks in the middle of the sea are the habitat of various seabirds such as cormorants, pelicans and booby birds. If you visit the arches it is very possible that you can see dolphins and orcas; and during the winter season, even some whales.