Don't know how old your Mac is, but my wife had to bring her ~2006-era MacBook in for free battery replacement at the Apple Store.
Water itself is not a particularly effective conductor; water with citric acid mixed in would have to be considered an efficient electrolyte, able to short out power components leading to battery overheating and failure I imagine.
Jagge is correct, such a situation can be dangerous. Here's a
video of a malfunctioning laptop battery...note that once this process starts, you really don't want to be anywhere close...6' flames. And the fire just gets worse and worse by stages. Note that a Class D fire extinguisher is required to put out a laptop fire once started; water will just spread the flames.