Can you find a way to sink treated 4x6 posts in the deepest part of the shallow pond where the walkway would be to allow some water flow between the two? To make a short bridge.....

What would prevent the rocks from slowly sinking down into the pond bottom over time?

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).