By Whistle
The UK distress signal is 6 blasts of a whistle, followed by a 1 minute silence, repeated until help arrives. The response for acknowledging help is 3 blasts, however, you should continue to signal for help UNTIL HELP ARRIVES.
SOS
Distress signals given off by lamp, voice or flag.
This is normally done in Morse Code using the following pattern
...---...
"."=Dot "-"=Dash, A dot is a short signal and a dash is a longer one.
RED flare
A red flare is fired to show that you need help and then is acknowledged by a white flare going off.