It could be possible that the energy I'm seeing from the same metal water batter is coming from temperature. The water could be cooler than the room, so the aluminum wire in the water is at a different temp than the one barely touching the water. The one barely touching the water is more at the room temp while the one in the water is cooler due to the water evaporating or something like that.
When I first started testing the same metal water battery I did try it with boiling water and got a much higher voltage than normal. When I fist started the most voltage I seen was around 200mV but the hot water gave me close to 400mV, that voltage was never seen before.