Totally backing up @the_elizabeth on this one. Saltwater gets into everything, and it eats stuff you wouldn't even think about. Those fancy coatings get scratched up from normal wear, and then you have a perfect spot for rust to start. On a ship, the whole unit is shaking and flexing for months on end, which just works those weak spots open. Even with regular checks, you can miss a small spot until it becomes a big problem. The sea itself absolutely is the main issue, because it never stops working against the metal.

David's got it right with server rooms. New gear means new cables and fresh chances for factory defects or ports that just don't seat right. Software only checks for logical signals, not if the physical link is barely hanging on. A rack getting bumped during install can cause problems that only show up when you reseat the cable.