A deadlight, within the context of marine terminology, refers to a robust protective covering or shutter designed specifically to be placed over certain openings, such as a porthole, on a ship or boat. These openings are generally used for lighting or ventilation purposes. The primary function of a deadlight is to secure these openings in unfavorable weather conditions or rough sea situations, to prevent the intrusion of water, harsh external elements, and to maintain the structural integrity of the vessel. They might also provide additional functions of security and privacy. This sturdy fixture plays a significant role in safeguarding not only the ship or boat, but also the individuals onboard.

1. "As the storm raged upon the sea, the captain ordered the crew to close the deadlights quickly to prevent water from pouring in." 2. "The sunset view from the cruise ship was gorgeous but as the weather turned stormy, passengers were advised to secure the deadlights." 3. "While restoring the vintage navy ship, they found the old deadlights, once used as protection from treacherous weather, to be in surprisingly good condition." 4. "In his round of the night safety checks on the old ship, he made sure all deadlights were firmly shut to avoid any disasters that might be brought by the rough weather." 5. "The sailors quickly moved to secure the deadlights on the submarine's portholes when they were ordered to dive deep to avoid detection."

Fun Fact: The top-notch survival horror game, Deadlight, borrows its name from an interesting maritime term. In maritime context, "deadlight" refers to a strong shutter fitted over a porthole or other opening that can be closed in bad weather to protect the integrity of the ship. It serves to keep the elements out while maintaining the ship's stability. In the game Deadlight, this concept takes on a metaphorical implication. The protagonist, Randall Wayne, shields himself from the harsh, zombie-infested world trying to survive, much like a ship in a storm using its deadlight. This clever use of terminology adds an extra layer of depth to the game's narrative, suggesting that even in the direst circumstances, there's always a means of preservation and survival.