A power-driven vessel during the day must display which shape?

A power-driven vessel is required to display a specific shape during the day to indicate its presence to other vessels. The correct shape is a cone with the apex down. This is part of the International Regulations for Preventing Collisions at Sea (COLREGs), specifically under the requirements for daytime signal shapes for various types of vessels.

The cone, displayed with the point facing downward, signals that the vessel is under power and aids in identifying the type of vessel. This helps prevent confusion on the water and enhances safety by providing other vessels with clear visual information about the presence and status of the power-driven vessel.

The other shapes listed, such as a cylinder, square, or diamond, do not correspond to the day shapes that power-driven vessels are required to display. Each type of vessel has designated shapes as per regulations, and understanding these shapes is essential for mariners to recognize the nature of nearby vessels accurately.