Usually putting together metal and water you get metal-oxide and hydrogen gas.
m + H2O → mO + H2
What they discover is a unusual zone where they have both oxygen (dissolved) and metal. So, i guess they have the reverse process :
mxOy + energy → (x)m + (y/2)O2
They should measure electrical field intensity in the water near the sea floor to evaluate electrical current going through the sea floor from the ocean.