#1: If at night, by use of a searchlight to send Morse Code. A regular flashlight will only work if you are in front of a very DARK background.
#2: Day or night: Radio Morse code.
#3: Daytime: Signal flags along your forestay or backstay.
#4: Daytime: Semaphore flag signalling.
#5: Day, or night with searchlight shining on it: Hang your country flag upside-down. This is the internationally-recognized sign of distress.
By radio or distress flares
FLy the flags upside down
By radio and flares
Send up a flare or hail local authorities on your radio.
Doing a mayday call over VHF is still the most common way to make a distress signal, however now all VHF sets have a DSC button which when hit send out an automatic distress signal to all receivers in range with location and distress information.
Radio and flares
Information can be transmitted through three main signaling methods: electrical signaling, chemical signaling, and mechanical signaling. Electrical signaling involves the use of electrical impulses, while chemical signaling relies on the transmission of neurotransmitters or hormones. Mechanical signaling involves physical interactions that convey information, such as touch or pressure.
While "of course" is the modern phrase, it began life as the phrase "as a matter of course" or "of the ordinary course". It was a term used in sailing in the 1500's.
BALLS
scarcity
Leif probably encountered some storms while sailing.
Variable