Question About Night Diving

[johnbar]

Hi All!

I just have a quick question about night diving that I haven't been able to get a direct answer anywhere. It is a multiple choice question from a diving exam...

"Lining up shore lights to form a _______ is an excellent means to help divers find the exit point."
a. Triangle
b. Range
c. Circle
d. Lubber Line

If you could explain as well, it would be very helpful!

Thank you!

 

[The Chairman]

Lubber line is a wrong answer, but I bet it's the one they use.

The lubber line is actually an imaginary line running parallel with the center of a ship. Also called the "Direction of Travel" it's usually represented by a double red line on your compass. What people don't realize that back in the day "lubber" meant "idiot" so it's really the idiot line.

So a lubber line is on a compass, but in this case, it would still be showing the idiots their way out.

 

[Texasguy]

Maybe a triangle? By making the figure you'd get a same perspective that is possible only from a same point of observation?

 

[tomfcrist]

The question is dumb. But the answer will probably be triangle...ie the shape formed by connecting the dots of the 2 lights and you...

Seriously...nobody does that crap.

 

[BRT]

Triangle. Line up 2 lights in one direction and 2 lights in another direction. That puts you at a single point. You are not going to use this.

 

[Marie13]

Triangle. SDI Night Diving book?

 

[halocline]

There's a night diving book? Does it have glow-in-the-dark text so you can use it on the dive?

 

[tomfcrist]

There's a night diving book? Does it have glow-in-the-dark text so you can use it on the dive?

Not likely, but it was probably written by an “expert” whose night diving experience has all been in a quarry.

 

[rsingler]

Sorry all! The correct answer is "range". It's an old sailing term used to describe two lights, one set behind the other , which when lined up, form a path in the channel to the harbor. See this picture:

In this picture, the viewer is to the left of the proper channel, because the rear/higher light is to the left of the lower range light. Turning to starboard on the way in will line the two up again. Hopefully you haven't gotten stuck in the mud this far off course!

So for diving, you need to find two shore lights that are distinct enough to guide you home, and are lined up one above/behind the other when you are facing the exit point. Then, all you have to do in the dark is swim to the left or the right until the two line up again, one behind the other. You will then be on the path you chose to get home. If you swim, keeping them in line, you will arrive at the exit point they were aligned with when you first chose them.

It's not a dumb question. Just uncommon. But try it and you'll then have a valuable safety skill should you choose to go night diving someplace with only a tiny exit beach tucked among the rocks. Of course, your judgment in choosing such a night diving spot may then come into question, but you can blow away your critics by describing the range lights and expert technique that brought you home in the dark.

 

[The Chairman]

49 years of diving, and this is new to me. I can't ever see having to use this "skill".