In Uganda, protesters are sprayed with colored water by the police, To identify and arrest them later. Many water cannons on the market today come with a tank specially designed to store a semi-permanent colored dye. If police decide they want to “tag” protesters with the dye, they can press a button to inject it into the main water stream. Once the water cannon is trained on a crowd, anyone hit by the spray will be easily recognizable by police. Uganda isn’t the only country to use dye in its water cannons: During the last 15 years, protesters in Hungary, Indonesia, Israel and India have all been showered with colored water.