Description: The Portuguese Man-O-War is found throughout the world in warmer seas, and is most common in the summer months in shallow coastal waters. It's name comes from the float, which is a gas-filled bladder that can be up to 12 inches long and 6 inches tall. The float is used as a sail to propel it across the water. Main food source is surface plankton but it can also take larger prey. Its tentacles have stinging cells called nematocysts that are capable of killing a fish up to 4 inches long. The poison secreted from the nematocysts of the Portuguese Man-O-War causes respiratory problems and muscle weakness. In humans, the sting of the Man-O-War can vary from extremely painful to incapacitating to fatal, depending on the severity and the victim's reaction.