Bahamas shipwrecks

[Oceanscience]

When we talk about shipwrecks in the Bahamas, we think about the past 500 years. How did the Bahamas look like 500 years ago?
What are the changes in altitude of the islands? Or should we say that the water level has risen by how much?
For example, the region where the "Maravillas" sank, was known as "Los Mimbres" which can be translated as "The Reeds". This suggests that there was some swampy area, where reeds were growing. There is no such thing nowadays. What happened? Did the land subside? Did the sea level rise?
How much?
How would this change the edge of the banks? It could very much change the tidal currents across the banks. The tidal currents have a strong influence on the shape of the sandy bottom.
Tidal currents can score out deep holes and in other places heap up sand dunes where a shipwreck, or parts thereof can get snagged. Changing shapes of the sea bottom due to changing currents, can later remove the sand and leave the wreckage on the hard pan bottom. More changing conditions can re-bury the shipwreck remains under many feet of sand.

The fact is, that the sand is easily moved by Hurricanes, Northers and in-numerous minute variations in weather patterns and sea level changes.

 

Amazon Forum Fav 👍

A History of Mining on the Kenai Peninsula, Alaska - Grab it through Amazon!

[Oceanscience]

With the remains of the shipwrecks, lying on the bedrock, buried under up to 15 feet of sand, we need to plan for specific equipment to uncover them.

Blowers can remove the sand, but every hole costs a lot.

How can we reduce the cost? Blowing fewer holes. If we can detect the remains of the shipwreck under 15 feet of sand we only need to blow a hole where there are remains.

The hard pan can be detected with a sub-bottom profiler.
Iron debris can be detected with a magnetometer.

What about silver bars, gold bars or even coins? How deep can they be detected?

What are the newest technological advances to be applied?

Are there metal detectors that can tell us the difference between an iron spike and a gold bar, 3 feet down?

Is there a detector available that can find a Piece Of Eight, 3 feet under the sand?

 

[aquanut]

OScience: "Is there a detector available that can find a Piece Of Eight, 3 feet under the sand?"


The Pulse Star would be a good bet.
Aquanut

 

[old man]

OScience: "Is there a detector available that can find a Piece Of Eight, 3 feet under the sand?"


The Pulse Star would be a good bet.
Aquanut

John, That's what I like about this forum. Guys helping others with equipment that most people don't know about and helping them out. By the way. I just found another 1 meter coil for the unit in my attic. So let pete know.

 

[Oceanscience]

OScience: "Is there a detector available that can find a Piece Of Eight, 3 feet under the sand?"


The Pulse Star would be a good bet.
Aquanut

John, That's what I like about this forum. Guys helping others with equipment that most people don't know about and helping them out. By the way. I just found another 1 meter coil for the unit in my attic. So let pete know.

Pulse Star, with a one meter coil. I can not find the underwater model.
We are talking about shipwrecks on the Bahama banks, maybe up to 50 feet deep.

What about tow-able metal detectors, can they find a Piece Of Eight under 3 feet of sand?

 

[Salvor6]

John and I use the Pulse Star one meter square coil underwater. It is waterproof and has waterproof connectors. I made a PVC sled filled with concrete to tow the coil behind our boat.

 

[stevemc]

I have a PI detector with a 1 meter coil. If you take the coil and twist it into a figure 8, and then lay it over so the coil is now about a 20 inch coil and the right impedence, it might find a cob. And of course the depth would be about cut in 1/2. So yes, you could use a 1 meter coil to find a cob, but it would have to be taken down in half. Mine will find beer cans at 6 feet in air, more in saltwater of course. A car at 25 feet in the air. The problem with large coil PIs, is first they are made to find things deep, deep is best at a low pulse rate, sometimes about 50 to 60 pulses a second. Plus if you had that large of a coil and a high rate of pulses, it would be way too sensitive-think of a coil as an antenna, it will pick up all kinds of EMI, and not work right in many conditions. Most underwater handheld PIs use a coil of 8" to 12" on average, and have pulse rates of 250 to 750 pulses per second. This is to find gold jewelry-the higher the pulse, the better it will find low conductivity metals/alloys - gold jewelry and in some cases Spanish cobs, which are mainly silver but often with a fair amount of copper. Those higher copper cobs are usually the ones that are fairly corroded, unlike nearly pure silver cobs, the copper makes the dissimilar metal problem and pits the cob. They are often green when found, higher silver are black. These higher pulse rate PIs will go quite deep on low conductivity stuff. Any higher than 750 pulses per second, and the saltwater makes it false real bad. Almost couldnt use it in the ocean. Some PIs do go up to 1000 pulses, but they are land units, and cant use too big of a coil. A PI with lower than 300 or so pulses per minute will have a hard time finding gold jewelry even quite close to the coil, unless it was fairly large. And like I said the average large coil PI has 50-60 pulses. Some UW PIs, like the J W Fishers 6 and 8, are low pulse rate PIs and wont find gold jewelry. And not go very far on a cob. But with there low pulse rate, are great at finding high conductivity metals, especially larger pieces, such as iron pipes, large pieces of iron and aluminum, but only as deep as the coil will allow. The larger the coil, the deeper it will go, but the size of the target will also have to be larger.

 

[Oceanscience]

Thanks for the feedback.
That sled looks nice. Is the Pulse Star a motion detector? I mean does it need to be moving to detect?
Would it make sense to incorporate an autonomous underwater detector, sled with one meter coil and a scooter for a diver to cover large areas?

The scooter, on a pivoting mount, could then also be used as a digging tool.

 

[aquanut]

OS,
We use the pulse Star to detect all metals. The great thing about it is that it discriminates between ferrous and non-ferrous while giving you the hit. We tie it in to the gps and dive promising anomalies with our the large coil and then remove overburden and pinpoint with our underwater handheld detectors, Aquapulse and CZ21's for example. I wouldn't concern myself with trying to make it a multi-purpose machine. It's not designed for that.
Aquanut

 

[wwwtimmcp]

jw fishers pulse 12 will and I a think the pulse 10 and the 4' coil for the pulse 8 will too, I also have a 16" hand coil that would probably find one. the smaller 8" coil with everything tuned and operating pefectly might but I'm not sure.

I have used my 4' foot coil attached to my pulse 8 for years and it has done me and jw fishers proud. I tow it behind my inflateable boat and stop on hits, I can stop the boat usually within 4' feet of the target. I drop anchor suit up and mark the spot on my gps just in case of drift,waves,wake etc.

I have found plenty of deep targets. one thing is to make sure your battery is fully charged. as the battery loses charge it loses sensitivity, but I have dragged the 4' coil for 8 hours with great results. the tomahawk head I found was under sand in between a deep rock crevace over 3' feet deep.

the smith and wesson pistol was found in another crevace covered with blue clay and about 2.5 feet deep. that was found with my 8" coil hand swinging in the water. I also found a 1918 walking liberty in yet another crevace covered by sand/blue clay mix by 8" coil by hand swinging in the water. the st. barbara medallion was over 24" deep under a stone 8" thick with abouth 18" of sand and clay on top of it.

hope this helps.

jw fishers customer service has been very good to me. I cannot say enough good things about them.

 

[FISHEYE]

Does anyone here have a extra fisher pulse 10 box laying around they want to sell as i have the fish and coil and cable,just no electronics.Even if i had some good detailed pics of the board with the components on it i can copy it.