BEIJING: China's Ministry of State Security said on Tuesday (Oct 29) that it had retrieved spying devices both on the ocean surface and in the depths of the sea, including underwater "lighthouses" that could guide the transit of "foreign" submarines. The ministry said it had uncovered devices that had been hidden on the ocean floor and were sending back information that could "pre-set the field for battle", in an article on its official WeChat account, China's most popular social media app.