Short Distance

A heliograph is simply a mirror with a hole in the middle that can be used to flash an S-O-S to boats in the immediate vicinity by reflecting sunlight. The hole is used to aid in sighting that the signal is hitting its intended target. There are models available that are small enough to attach to your paddling jacket or even store within one of the pockets on your PFD. In a pinch, if you have a CD on board, you can use it to reflect the sun and use the hole for sighting purposes.