The Master of a small passenger vessel fitted with loading doors must ensure that the doors are closed, watertight and secured __________.

Correct Answer: Option C — at all times when underway unless operating on protected or partially protected waters

46 CFR 185.340 requires that loading doors on small passenger vessels remain closed, watertight, and secured while underway, except when operating on protected or partially protected waters. This prevents progressive flooding and maintains the vessel's reserve buoyancy and stability during transit in more exposed, hazardous sea conditions.