Sailing at night, colloquially... night sailing.
Night sailing—it's not just a simple term.
In this world, similar to the medieval era, where nautical skill is extremely primitive, it's not just that there's no modern Earth GPS or radio communications; there aren't even Sextants to calculate longitude and latitude, nor accurate sea charts.
You should know, in the history of Earth, nautical technology didn't leap forward until after the medieval era, in the Age of Discovery. Under the temptation of immense wealth brought about by geographical discoveries, there were substantial developments in shipbuilding, astronomy, hydrology, navigation, and trade.
