May 20, 2013 at 1:30 AM
Note how it turns a different colour after being out of the water for so long.
And for all we know, it might not have been that long between when the Core was teleported to the lab and when you find it in the Black Space. The unconsciousness before waking up with Curly's air tank, before waking up in the Mimiga Village after the Waterway, and in Jail No. 1 could have been some time, but they also could have been brief for all we know (I've never seen any extensively solid implications that any of them were very long).