Signal passing vessels using a CD’s reflective power
Any survivalist knows that sometimes calling for help is the only way out. For those cases, it is helpful to have an object that can be used to signal from far away. Any reflective item can be used to make signals with light.
A CD or a regular mirror will work. Bring the CD to your eye and angle it so the reflection hits your finger. Keeping that angle, move the digit until it points towards the vessel that your efforts are trying to call over.