SEND AN SOS
Three dots, three dashes, three dots is the formal distress signal used in Morse code. Flash it at night with a flashlight, or follow up three short whistle blasts with three longer ones and then three more short ones. You can also spell out the letters SOS on open patches of sand, rock, or snow, using stones, branches, logs, kelp, or other debris that boldly contrasts with the background. Other useful symbols include I, which means you have an injured party; and X, which means you can proceed no farther.