Naga fireballs (Thai: บั้งไฟพญานาค; rtgs: bang fai phaya nak), also known as Mekong lights, and "bung fai paya nak" by the locals, is a phenomenon said to be often seen on the Mekong River. Glowing balls are alleged to naturally rise from the water high into the air.[1] The balls are said to be reddish and to range in size from smaller sparkles up to the size of basketballs. They quickly rise up to a couple of hundred metres before disappearing. The number of fireballs reported varies between tens and thousands per night.[2] The phenomenon is named after the Phaya Naga, legendary serpentine creatures said to live in the Mekong.