Oak Island

Some accounts state that Smith used it as a fireback in his fireplace, while others claim it was last seen as a doorstep in a Halifax bookbinder's shop. The accuracy of the translation, whether the symbols as commonly depicted are accurate, or if they meant anything at all, remains disputed.
Man made structures under Oak Island do in fact exist as discussed in many books, including a book written by Lee Lamb, daughter of Robert Restall. Whether these structures are the remains of prior excavation attempts or artifacts left behind by those who allegedly built the Money Pit are unknown. It is known that several documented post-1860 treasure recovery attempts, as described above, ended in collapsed excavations and flooding.
Pirate treasure
Some believe the pit holds a pirate treasure hoard buried by Captain Kidd or possibly Edward Teach (Blackbeard), who claimed he buried his treasure "where none but Satan and myself can find it." Some also hold to the theory that Kidd conspired with Henry Every and Oak Island was used as a pseudo community bank between the two.
Naval treasure
Others agree it was dug to hold treasure but believe this was done by someone other than pirates, such as Spanish sailors from a wrecked galleon or British troops during the American Revolution.

During the French Revolution, when the Palace of Versailles was stormed by revolutionaries in 1789, Marie Antoinette instructed her maid or a lady-in-waiting to take her prized possessions and flee. Whether such a complex engineering effort could have been completed in that small space of time is questionable, though no official date of its construction exists.

However, other theories do suggest the structure is French and naval in style.
Exotic treasure
Still others have speculated that the Oak Island pit was dug to hold treasure much more exotic than gold or silver. It is argued that the story of the money is largely unverified and the gap of sixty years between the supposed discovery and the first known reports is very long.

Indeed, it is noteworthy that no debris, lost tools or other items mentioned in the early accounts have been found with the exception of the sheepskin parchment, the heart shaped stones, and the stone triangle.
Joe Nickell also identifies parallels between the accounts of Oak Island and the allegory of the "Secret Vault" in Freemasonry (similar to the Chase Vault), and identifies many prominent excavators as Freemasons, leading to the suggestion that the accounts explicitly include Masonic imagery.
Sinkhole
Suggestions that the pit is a natural phenomenon, specifically a sinkhole or debris in a fault, date to at least 1911. There are numerous sinkholes on the mainland near the island, together with underground caves (to which the apparent booby traps are attributed).
The appearance of a man-made pit has been attributed partly to the texture of sinkholes: "this filling would be softer than the surrounding ground, and give the impression that it had been dug up before", and the appearance of "platforms" of rotten logs has been attributed to trees or "blowdowns" falling or washing into the depression. An undetermined pit similar to the description of the early Money Pit had been discovered in the area. Then logs of spruce and oak were unearthed at irregular intervals, and some of the wood was charred.

The immediate suspicion was that another Money Pit had been found."
Romanticized elements
Many elements contained in the Oak Island story, such as the discovery of tantalizing but inconclusive objects and a message in indecipherable code, are common in fictional works on treasure and piracy (such as the Edgar Allan Poe short story "The Gold-Bug"). This has led many to conclude that the early account of the Money Pit is a romanticized combination of several works of nineteenth century fiction conflated with a local story about a search for buried treasure.
Similarly, the burial of the supposed jewels of Marie Antoinette requires, logically, an assumption that they would someday soon after their concealment be retrieved.The apparent complexity of the Island's 'treasure' structure seems too frivolous an attempt to conceal what the queen's maid could have easily used for her own gain once in North America. This type of limestone easily dissolves when exposed to water, forming caves and natural voids.

He stated in a letter to author D'Arcy O'Connor on 21 October 1976 that his drill operators encountered what appeared to be a natural cavity after drilling through approximately 2 feet of limestone at 141 feet. His professional opinion at that time was that the Windsor limestone formation had been struck.

This is the only known scientific study that has been conducted on the site. After running dye tests in the bore hole, they concluded that the flooding was caused by a natural interaction between the island's freshwater lens and tidal pressures in the underlying geology, refuting the idea of artificially constructed flood tunnels.

The Woods Hole scientists who viewed the videos taken in 1971 concluded that nothing conclusive could be determined from the murky images.
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