Ancient Sunken Harbors near Tampa Bay, FL

Tampa Offshore Ancient Sunken Harbor

Above image-photo is a composite of Satellite Imagery and Google Earth of the Tampa Offshore Sunken Harbor, and is used with permission and/or used under 'public domain' and 'fair use' policies due to the nature and content of this book being research and education material. The coordinates in Google Earth are: 27°37'39.27"N, 82°47'32.17"W. Set 'Historical Imagery' to 11/12/2007.

Based on the size and length of the Tampa Offshore Sunken Harbor as a major engineering project, a population base large enough to have ready resources to undertake the massive construction components of this size project is required. To complete other massive projects here in Florida, as well as New York, Mexico and South Africa, around the same relative time frame suggests a major Atlantic rim population density.

The Tampa harbor is located about 2.2 miles offshore in the open ocean. It rests on a high tidal shoulder beside a large land egress channel. Length of the main body of the harbor is something over 9,000’ to 10,000’, with a widened harbor to the left, and an additional 3,000' exit canal toward the open ocean. Based on harbors of similar sizes today, we can estimate the depth of the cut harbor to be 35' to 45' deep.

The volume of material cut, transported and disposed was roughly 45,000,000 (forty five million) cubic yards. At an average cost in dollars today of about $12 per cubic yard, this project looks like the beginning of a colossal engineering project in the $538,000,000 (MILLION) dollar range.

At this level of material, a minimum of technical machinery including dredge cutters, piping, barges and a whole range of equipment would be required. Although mega projects of this size have been accomplished in the past, using manpower alone, (such as the great wall of China), nothing on this order has ever been shown to have been done in the cutting and dredging of harbors of this size, while at the same time being involved with several other like projects, as demonstrated by the Boca Grande Harbor, (about 70 miles south), and other similar sites. Based on casual observation alone, it is evident this harbor was not completed with manpower alone, but with some very sophisticated machinery and equipment.

Ocean depth at the tidal shoulder (edge of the harbor) is estimated to be between 6’ and 9’ deep, but could be as much as 12’ to 15’ deep. Those depths place a date certain, based on Ocean Level Rise, of between 7,200 and 7,400 years before present.

There is no shore based use for this large a harbor. It is not 'landfill' as that process is done much closer to the shoreline. There is no records available of any Corp of Engineer work being done in this local area that can be found.

We think that this civilization was destroyed by a super mega cataclysm, and if so, it is entirely plausible, if not likely, that some residue artifacts in stone, pottery and possible other unknown materials, are preserved in the mud and silt at the bottom of this harbor. We intend to be the first to find out. We are NOT releasing location coordinates on this site pending our own expedition dive. If you are interested in joining the expedition to this site, please let us know.

Boca Grande Harbor

Above image-photo is a composite of Satellite Imagery and Google Earth of the Boca Grande Harbor and causeway, and is used with permission and/or used under 'public domain' and 'fair use' policies due to the nature and content of this book being research and education material. The coordinates in Google Earth are: 26°42'29.97"N, 82°17'9.41"W. Set 'Historical Imagery' to 4/1/2010

In addition to this amazing underwater artifact, there is an existing causeway or roadway that extends from the harbor edge northeast, terminating at the secondary tidal shoulder of the current shoreline. As a rough estimate, this structure as an engineering project would consist of cutting, dredging, removal and disposal of approximately 8,100,000 cubic yards of material. Total project cost in today’s dollars of roughly $6 per cubic yard of material means this project had a budget of just under $50 million dollars.

The Boca Grande Harbor sits on the secondary tidal shoulder and appears to be in the range of 6’ to 9’ below current mean tide level. If so, that means its relative build and use date had to be within a very tight window between 7,200 and 7,300 years ago. At that time, the Third Meltwater Pulse Ocean Level was rising at the rate of more than 5’ per 100 years. Since Ocean Rise is established to be slightly more than 5 feet over the last 7,000 years, an additional 3-5 would indicate a depth of 6-9’ to be roughly equivalent to 7,200 years ago.

Above image-photo is a composite of Satellite Imagery and Google Earth of the Boca Grande Harbor and causeway, and is used with permission and/or used under 'public domain' and 'fair use' policies due to the nature and content of this book being research and education material. The coordinates in Google Earth are: 26°42'29.97"N, 82°17'9.41"W. Set 'Historical Imagery' to 4/1/2010

The road or causeway that extends from the harbor northeast to the shoreline is about 2.0 mile long, and is degraded and covered over with sand in several places. This section is more degraded closest to the harbor proper, and then retains its original shape of the section closest to the shoreline. 

This harbor has many features similar to the Tampa Bay Sunken Harbor, both are very near or on the edge of a deep water channel that goes out through the continental shelf to the open ocean. Edges of the harbor edge or shoulder are currently estimated to be between 6' and 9' beneath mean tide ocean level. Its depth suggests it is contemporary with the Bimini Road as well as other Harbors and canals at this depth. Ocean level rise dating suggests this Harbor was inundated between 7,000 and 7,100 years ago.

North Key Largo

Above image-photo is a composite of Satellite Imagery and Google Earth of the North Key Largo complex, and is used with permission and/or used under 'public domain' and 'fair use' policies due to the nature and content of this book being research and education material. The coordinates in Google Earth are: 25°13'22.54"N, 80°20'23.09"W. Set 'Historical Imagery' to 11/12/2007

This site is a series of inlet canals that are grown over and silted in, eroding back into the landscape. The center canal is one of the largest (if older) ones found to date. It is about 2,700’ long to the end of the ‘silted in’ paddle head. The original width is about 350’ and the newer section is about 170’ wide. The old section of the south canal is about 445’ wide, and the newer section is about 220’ wide, the north canal is about 85’ wide.

The curved S sections connecting the canals are completely silted in and grown over. To the right, an unused, unconnected cut canal goes out to open water. There is substantial berm around the open water cut canal, indicating it was built when the tidal shelf was above water. Of significance is the moat canal surrounding this complex. All indications are that this complex is one of the older shore based complex systems found to date. It certainly may not date to -7,000 ybp, but it is much older than the 200 odd years our modern culture has been settling the South Florida Keys. It may very well postdate the offshore Harbors. Berm soil samples need to be taken here for a relatively accurate C-14 dating sample.

This complex appears to have two building and use periods, one that is less structured and has the appearance of being built on top of the old system. The original berm on this center canal includes the large rectangle paddle head. The second berm seems to have been cut out of the silted over section. It is not possible in this preview, to do justice to the many features of this complex, and much field work is required to make serious statements of potential purpose and function.

I will agree this complex does not appear to support a 5' rise in ocean level, but it certainly could and would support a 1" plus raise, putting the date of this complex somewhere between 4,500 and 5,800 years ago. In any case it is not modern, meaning it was not built in the last 200 or so years of Florida expansion. There are many other shore based complexes in the Keys that show at least a three tiered tidal shoulder that is about 2' deep.

In the next section, we will look at the complete Long Island Sound channel and offshore harbors system.