"Being a nuclear sub doesn't mean that we're not as vulnerable to underwater hazards as the older ships," Benson said.

Acoustics were greatly improved upon during World War II so as to be used as a tool to detect unfriendly vessels and underwater hazards.

This was a dangerous coast as, flat as it looked, a few miles out to sea unrelenting sandbars paralleled the shore; underwater invisible hazards, shipwrecking the unwary.

Last month the Norwegian authorities proposed entombing the submarine in a watery sarcophagus, as has been done elsewhere with underwater hazards.

The wreck was moved in August 1979 to render it less of an underwater hazard.

The underwater hazards of the river change from year to year.

We charged across the deck, launched ourselves at the frames, and clung on for dear life as the ship tipped quickly like a spinning top, waltzing between the underwater hazards.

A hydrographic chart will obscure the actual features to present a simplified version to aid mariners in avoiding underwater hazards.

Operating in stealth mode, they cannot use their active sonar systems to ping ahead for underwater hazards such as undersea mountains, drilling rigs or other submarines.

The Moiré effect is used in shoreside beacons to mark underwater hazards (usually pipelines or cables).