OK... it's DEFINITELY water in the tank. I syfined out about 8 gallons, and the last gallon was ALL milky and not gaslike. Smells very faint, too.
Now the problem is I can't seem to syfin out the rest of the gas. There's still just over half a tank in there, and my hose just come's up hitting air. I just tried to drain the tank via the plug underneath, and it stripped. F@ck.
I guess I'll keep the syfining up and hopefully make some progress.