Staring Into the Abyss

It probably takes a good half-hour to go from the slip out to the inlet and then the open sea; and then another good hour out to the wreck site. So I was sitting on the dive boat, staring out into the ocean and back towards the waning land, debating whether I wanted to try to catch a few extra minutes of shut-eye or to shake the early morning bleariness from my eyes. Then I was startled by the sound of a lawyer saying, “This is pretty eerie, huh.”

“Yeah…Ironically, isn’t this how the City of Athens went down?”

Only a few miles from the Jersey shore, we had suddenly found ourselves in a patch of dense fog. Sitting on the deck, you could only see about 30-feet in any direction. And I started to think about how we were motoring full speed through fog with near-zero visibility, for the sole purpose of scuba diving on a ship that was struck by another vessel and sunk under what I can only imagine were similar conditions.

Much to the chagrin of wreck divers everywhere, leaps and bounds have been made in early detection and observation systems in the past hundred years…It was in the early 1900’s that Nikola Tesla (give or take a few years and scientific cohorts) began working with primitive radar systems. And it was at the footsteps of World War II that the true predecessors of modern radar came online.

Standing on the deck of a small boat in good visibility, the distance to the visible horizon is only about five miles due to the curvature of the earth. In this day and age, it is commonplace for large ships and planes to be equipped with powerful radar systems that alert them to far-off objects and conditions that couldn’t possibly be seen by the naked eye – even on the clearest of days. It is now even possible for planes to land in heavy fog. If an airport is equipped with radar-assisted ground-controlled approach (GCA) systems, a plane’s flight can be observed on radar screens while operators radio landing directions to the pilot.

And much to the chagrin of hard hat divers everywhere, leaps and bounds are being made in underwater detection and surveying.

Sidescan Sonar

Sidescan Sonar is a system that is used to create an image of large areas of the sea floor. This tool is used for mapping the seabed for a wide variety of purposes, including creation of nautical charts and detection and identification of underwater objects. The Castle Group has owned and operated a JW Fisher Side Scan Sonar system for a few years now; and in my humble opinion, the output images aren’t that impressive…

…until I think about the fact that it can make reasonably accurate images and measurements of a sea floor that is several hundred feet below the water surface. It’s actually quite impressive.

With a sidescan sonar system mounted on a small boat, a large area of a river bottom can be scanned in a short amount of time, the resulting images can be displayed on a monitor in real time, and items such as scour holes, utility cables, and debris can be located quickly and efficiently.

Multibeam Hydrographic Survey

In the 1990s, sonar was being brought to a whole new level. Like the name suggests, Multibeam Sonar sounders emit multiple “beams” of sound waves in a fan-shaped pattern to produce a swath of sounding data in a single pass over an area of the seafloor. With Multibeam Hydrographic Surveys it is possible to clearly depict scour holes, underwater cable runs, and debris with striking results.

The image above shows the results of a Multibeam Survey around a pier just off the Delaware River. It clearly depicts the navigation channel, scour holes in the river, cable runs shooting across the river bottom, and one can even start to see how the flow patterns around the piers are affecting the river bottom.


…Our small craft finally broke out of the fog; and once again I was left staring at nothing or whatever it was that my imagination told me was out there.

A day or two after the dive trip, my electronic travels brought me across another blog that I thought interesting and
worth excerpting…

“…night watches are my favorite part of the twenty-four hour day…I stood on bow watch scanning the horizon enjoying the warm breeze run through my hair. Visibility was perfect. Far off, about one point on the starboard bow, I could see a minuscule white light. I waited a few minutes until I was sure it was a light and not a star, and reported it to my mate, Mr. Dimock. He confirmed the light and we went below into the dog house to look on the radar. I was right, a ship of some sort was out there, and holding a course towards us.”

Sam Brown, Night Watch, 10. 24. 09


~ by castle2268 on July 16, 2010.

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