Wonders of Diving

Many articles are written describing beautiful diving destinations. Dive sites containing natural swim throughs, gazebos, even chimneys created by coral reefs. Glorious wonders of diving.
This article is a bit different. This article addresses practices that make you wonder where they originated.

Knots of Speed
Many people wonder how speed on the water came to be referred to in knots. Some people believe that this is rooted in a shortening of the term nautical miles…well, yes and no. Prior to the term ‘nautical mile’, sailors coined the term sea mile-then later the nautical mile. Even this had rather ambiguous beginnings.

Early mathematicians had worked out the approximate size of the earth and a nautical mile was to represent one minute of arc along a great circle. There was a problem however; different mathematicians had varying distances for this.

After much debate over centuries it was finally settled and became an international agreement that a nautical mile should measure 6076 feet. Which is nearly equal to a minute of latitude on a nautical chart.

Prior to the global positioning system (GPS) mariners needed to know when they reached a nautical mile of travel. So they devised a unique system to measure speed.

According to Wikipedia the first system was as simple as throwing a floatable object overboard and using a sandglass to measure the time it took to travel between two points.

This method was not exactly accurate, so our clever sailors developed a better system. This system was known by more than one name. A ships log, a chip log, or a knot log. For the purpose of this article we will stick with the term Knot Log.

The knot log consisted of a spool of line, a chip, and a sandglass. The line contained knots spaced at 47’3”. The chip was a piece of wood shaped like a quarter of a circle and weighted at one end to hang perpendicular to the surface of the water to create drag. The sandglass measured time in a 28 second capacity.

How it worked is the bitter end of the line was attached to the chip. The chip was dropped over the stern of the vessel. Once this action occurred the sandglass was inverted. While the sand dropped through the glass the line slipped through the sailor’s hands. The sailor’s counted the knots until the sand ran out-thus determining the vessels speed by knots.

The term knots is still in use today for nautical purposes. The speed of a vessel, the wind, and currents are measured in knots.

Fathoms
Not commonly used today but seen on nautical charts is the term fathom. A fathom is measurement of depth equal to six foot. The term itself comes from the Old Frisian term “fadem” meaning a pair of out stretched arms.

Diver Down Flag
Ever wonder how the dive flag design came to be? According to Florida Dive Connection Denzel J Dockery “Doc” living in Michigan at the time was looking for a way to warn boaters of a divers presence.

Doc became familiar with the solid red Baker flag that was used to signal danger while he was in the Navy. He used the flag as a base, with his wife, Ruth sewing white stripes on the flag.

Initially Ruth sewed a horizontal white strip across the flag. Discovering that was the same design of the National flag of Austria, they shifted the stripe to stretch from the upper left corner of the flag to the bottom right corner. The modern diver dive down flag was created. In 1956 US Divers began distributing the flag through out the country.

Doc, with the help of Michigan dive club Cuadro Pescadores, convinced the state of Michigan to adopt a dive flag law. Michigan was the first state to do so. Ruth had her hands full sewing dive flags.

Many resources we use today in diving came from centuries ago while others have developed in recent decades. Even with technology replacing old methods the terminology remains the same.

I hope you have enjoyed my articles as much as I have enjoyed writing them. I would like to thank Island Jane for including me in their family over the years.

Remember-Dive safe and often!

Tracy Brenner has been a resident of the Florida Keys since 2002. Tracy owns and operates Abyss Dive Center in Marathon. Tracy’s scuba instructor rating is a PADI Course Director. She is an Instructor Trainer for Divers Alert Network and a Diving Safety Officer for the American Academy of Underwater Sciences.