Re: Is it possible for crystals to have large min./water bubbles in them?

In answer to your question -- Quite simply YES.
Hydro agates do exist and I've seen some fine examples as do crystals 
with little bubbles therein. The water is not injected.

I believe that the water will never (in a million years) form a complete 
hard centre. In processing such agates it is very important not to breech 
the bubble walls as the trapped water would escape. Then all your left 
with is an agate geode.

Alec McCreadie