Is it possible that there could be a dry cavern(s) deep beneath the ocean?

Question

i'm just looking for a yes and a brief "why" or a resounding NO. you're an idiot etc etc.

Answer 1

it's possible.  Although most sea sediments including limestones and shales have minute permeability making the situation impossible, certain anomalies may exist involving salt, for example, which is impermeable, but could have formed caverns at some point in history.

It's pretty unlikely, but possible.

Answer 2

No.

1/ You will need an impervious layer to protect it. Else the water is saturating all the pores of the rock under the sea. I do not see the reason why a cave will not be filled with water.

2/ Even if you have an impervious layer, and I only see salt which can work, the pressure will make the salt flow in the cave or the cave will collapse !