During the great expeditions to discover and map the whole world, countless ships were deployed in order to raise the chances for the mission. The rise in sea travel also saw the advent of pirates using military and civilian ships just so they could plunder merchant and treasure fleets going around the world. These ships were identified using the flags that they bore.

Pirate ships used different flags in order to mark their ships. They used modified street banner types in order to maximize the image that they wanted to display. After all, these pirates also had different principles that they stood for. They also wanted to frighten the crew of the targeted ship as part of their boarding strategy. The main thing to look out for would be when the pirates would fly their colors. This usually meant that they were ready for a fight and that they would not back down. This frightened a lot of crewmembers and allowed the pirates to be successful in their mission.

These days, the flags are used to mark registered sea craft. This is because the ones that don't have registered markings are classified as hazards in the water. The ships these days use custom flags that show their insignia and sometimes, the nation that the ship sails under. This method of identification is one of the more reliable ones since these flags are easy to spot and record. Moreover, they can be used as landmarks when searching for something on the vast expanse of water.