Spear guns are the most environmentally friendly way to fish for food with zero by-catch or ghost gear unlike other fishing methods. Spearguns come in two options: Sling or Pneumatic. Sling guns use a rubber bungee under tension to propel the shaft through the water. Pneumatic guns have an internal barrel that connects to a separate chamber filled to a pressure of about 20bar. Pushing the spear into the barrel compresses the separate chamber closer to 35bar that is used to fire the shaft.