Which of the following is NOT one of the four primary types of anchors?

The statement identifies "storm anchor" as the option that is not considered one of the four primary types of anchors used in maritime practices. The four primary types of anchors commonly recognized are the stockless anchor, fluke anchor, plow anchor, and the grapnel anchor, each designed for specific holding capabilities and seabed conditions.

The stockless anchor is designed for easier handling and is commonly used on modern vessels due to its ability to set quickly and hold well. The fluke anchor has prongs that dig into the seabed for better holding power, often used for smaller boats. The plow anchor is shaped like a plow and is effective in various seabed conditions because it can penetrate and hold firmly.

While "storm anchor" may refer to a type of anchor used in severe weather conditions, it is not categorized among the primary anchor types. Instead, storm conditions are generally handled by using larger and heavier versions of the primary types mentioned, which are better suited for ensuring stabilization and safety during rough weather. Understanding the design and purpose of each recognized anchor helps in choosing the appropriate equipment based on the vessel, environmental conditions, and anchoring requirements.