User blog comment:Lord Loss/Monster Hunter Theory... Blog/@comment-4697011-20120917144957/@comment-1011548-20120918064532

Sea water is more conductive than fresh water because of the conductive dissolved salt in it. Pure H20 is actually an incredibly poor conductor of electricity.

And yeah, Lagiacrus doesn't fry the whole ocean because the ocean is very big and the charge disapates very quickly.