Item description:

Oceans have an 'infinite' amount of water, this is necessary for your computer to run it. Any water disconnected from the ocean and low in mass will be finite and react to changes in volume. If you break a border wall inbetween the lake and a cave, the lake will flood downward and drain out. Sponges are randomly generated on the map. They will appear underwater. They absorb a lot of water if the sponge is placed below it and they can be squeezed dry.
Water grates allow water to pass through, they can be 'closed off' with a redstone input.
Water sensor blocks activate connected redstone when a neighboring block is finite liquid.

Methane will generate underground. Methane either catches on fire or explodes