Mantas are found in temperate, subtropical and tropical waters. Both species are pelagic; M. birostris migrates across open oceans, singly or in groups, while M. alfredi tends to be resident and coastal. They are filter feeders and eat large quantities of zooplankton, which they swallow with their open mouths as they swim. Gestation lasts over a year, producing live pups. Mantas may visit cleaning stations for the removal of parasites. Like whales, they breach, for unknown reasons.
Both species are listed as vulnerable by the International Union for Conservation of Nature. Anthropogenic threats include pollution, entanglement in fishing nets, and direct harvesting for their gill rakers for use in Chinese medicine. Their slow reproductive rate exacerbates these threats. They are protected in international waters by the Convention on Migratory Species of Wild Animals, but are more vulnerable closer to shore. Areas where mantas congregate are popular with tourists. Only a few aquariums are large enough to house them. In general, these large fish are seldom seen and difficult to study.
Swimming next to a manta ray is a great privilege, because she is one of the giants of the ocean, the manta rays can measure eight meters and weigh 1400 kilograms, recently we learned that they are family of sharks.
We know very little about the manta ray, they are a mystery, because they can't live in an aquarium. The greatest danger to the manta ray is the fishing harpoon. But the manta rays are still a really mistery.
Source: YouTube, Extreme Nature, and Wikipedia