(ET) Deep Cycle Battery Question

[Klein Robert W NPRI <KleinRW Npt NUWC Navy Mil>]

A buddy of mine gave me a 12v wet cell Deep Cycle battery from his boat.  
Said it wouldn't hold a charge.  I took it home, pulled the caps and saw 
dry plates.  Added distilled water and EDTA and hooked it up to my monster 
military surplus charger and gave it a good long equalizing charge.  It 
was a clearly audible charge with bubble actions in each cell.  
Periodically, I checked the state of the battery with my "toaster" load 
tester and hydrometer readings.  All indicated good condition.

My question is this:  I've had the battery off charge now for a couple of 
days and when I put my ear close to the battery I clearly hear the 
bubbling.  I pull the covers and see the bubbling.  It's not much but it's 
constant.  The toaster meter and hydrometer readings remain good.  My 
concern is that there's something going on deep inside the battery that 
will continue to breakdown the H20 thereby causing the battery plates to 
dry out again.

Thanks in advance,

Bob