However, early Netherlandish painting in the 15th century was the first to make oil the usual painting medium, and explore the use of layers and glazes, followed by the rest of Northern Europe, and only then Italy.
An American flag or for that matter any flag flown upside-down is considered a sign of distress... US Code:T36 Ch10.176. (a) The flag should never be displayed with the union down, except as a signal of dire distress in instances of extreme danger to life or property.
Diver down flag. A diver down flag, or scuba flag, is a flag used on the water to indicate that there is a diver below. Two styles of flag are in use. Internationally, the code flag alfa/alpha, which is white and blue, is used to signal that the vessel has a diver down and other vessels should keep well clear at slow speed.