undersea

These could allow China to carry out surveillance deep underwater and detect other submarines or even undersea cables without risking its own naval forces.

Besides landing on Taiwan's beaches or launching missile attacks, it could also stage air and sea blockades, or sever undersea communication cables.

The Faroese prime minister says Shetland could boost growth and revitalise island life by following his country in replacing ageing ferries with undersea tunnels.

In their enveloping blueness, dotted with colorful fish and coral reefs, the undersea scenes are, in fact, quite meditative.

Critical infrastructure such as undersea cables would "continue to be a target", the document added.