See the perfectly round dark dot almost on the middle of this pic? Well, it is said is a Pirate mark on Las Marietas Islands, in Riviera Nayarit, just in fornt of Punta Mita. The fact is that bellow that spot, under the water, there is the entrance to what scuba divers call the Bubble Cave. If someone's dive into it, will find a gallery that can be filled with the air divers exhale. They can even take out their masks in order to feel like they are off the water, but they must never leave the regulator 'cause that air is pure carbon dioxide from the exhalations. That being said, explains the tale that says that ancient pirates in Riviera Nayarit, looking to robe the Nao from China, marked the entrance this cave with a canonball shot as a boobie trap for the hidden treasures. That way, divers trying to steel from that cave would feel safe to breath once in there and die after inhalating toxic air.