Removing silt from underwater cave entrance

[Tratt]

I posted in another section about this subject and I think it was a wrong thread, had to be about Montezuma in general, but it was about Victorio Peak, oops.
http://www.treasurenet.com/forums/victorio-peak/3366-what-current-theories-17.html#post4283372

Does anyone have ideas how to cost-effectively and reasonably fast open the entrance to the cave mentioned in that post, without draining the lake/pond because that was specifically forbidden.

 

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[H-2 CHARLIE]

Drain it for complete wrecklamation and over see the project .

 

[Tratt]

Drain it for complete wrecklamation and over see the project .

Draining was specifically forbidden - Scott Wolter suggested it to the land owner in his show. A more powerful dredge seems like the obvious answer then.