On the appearance of wet footprints do you:
a) assume the kids have spilt something
b) assume that heavy rainfall has flooded the garage
c) realise that the water heater is leaking
That'll be the water heater then, a 50 gallon monster of a water heater.
and that'll be the hole in the wall needed to replace it. Good job they're built to last, they reckon that the new one will be good for all of, er, 9 or 10 years...