Just as Plausible as anything else...
The Island was higher above sea level when the treasure was buried. They constructed a wall or barrier in case of storms until the miners finished the tunnels with slave labor. If you go to the lowest area to construct your tunnels under a hill you do not have to dig as deep. Plus you can go in at a predetermined angle to achieve the depth you want. A shaft is never a save place to hide a treasure without another entrance. The shaft was only used to lower the treasure. Then it became a trap for anyone seeking to recover the treasure without knowing exactly how to go about it.
"From the Akashic Records of Thoth:
"In the ancient days of the Mazur, after the death of Atlantis, these
people came to the region of North America that is now Nova Scotia.
They brought with them the 'Green Sea' Stone, one of two of the
original 'Right to Rule' stones which had been given to their first
generation by Melchizedek in Lemuria and brought with the Grail Family
from there into Atlantis. The other half of the stone, the Emerald
Table, was by then in the keeping of Thoth Raismes (an incarnation of
Melchizedek). This latter would eventually be placed upon the vault
of Osiris beneath the Temple of the Risen One (Giza) in Egypt. (Note:
these two stone slabs are not to be confused with other ancient Right
to Rule stones, such as the 'Stone of Destiny'.)
"The Mazur were led by their Wise Man or Seer to an entrance which led
into the recesses of the Earth, wherein were located a large labyrinth
of natural caverns. It was in these caverns that the Mazur placed the
sacred things which they had managed to salvage from the Deluge,
including the Green Sea Table of Melchizedek. After awhile, the Mazur
left this location after having sealed away most of their sacred
relics and tools of power within the caverns. Before they crossed the
sea into Great Britain and eventually the European continent, they set
up an 'initiatory entry field' upon a hill over a tunnel into one of
the sealed caverns.
This hill would later become an island -- Oak
Island in Mahone Bay. The Oak Island pit and lesser, man-made
labyrinth was never intended for physical entry. It was put into
place as a passage of Spirit Initiation. When the initiate 'passed
the tests,' he would be given the knowledge as to the location and
means to access the actual physical entrance to the sealed caverns
below. This physical entrance is not on the island, but some miles
away, on the mainland of Nova Scotia. Since that time, several
different peoples with partial knowledge concerning the sealed caverns
of the Mazur have reinforced and added to the original design of the
'initiatory field' on Oak Island.
Your Bud Aurum