Usually putting together metal and water you get metal-oxide and hydrogen gas.
m + H~2~O → mO + H~2~

What they discover is a unusual zone where they have both oxygen (dissolved) and metal. So, i guess they have the reverse process :
m~x~O~y~ + energy → (x)m + (y/2)O~2~

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.