A small passenger vessel operating on exposed or partially protected waters may not have a port light below the weather deck unless __________.

Correct Answer: Option A — its sill is at least 30 inches above the deepest load waterline

46 CFR 177.300 dictates that port lights located below the weather deck must have their sills at least 30 inches above the deepest load waterline. This height provides a critical margin of safety against downflooding, ensuring that the vessel remains watertight even if the port light glass is broken.