What characteristic defines a Fluke style anchor?

A Fluke style anchor is characterized by its unique shape, which includes wide flukes that create a large surface area when set in the seabed. This design allows it to dig into the bottom more effectively, providing superior holding power, especially in sand or soft mud. The flukes help the anchor to be securely buried in the substrate, increasing resistance to being dislodged by wind or current.

The other options suggest characteristics that may apply to different types of anchors or boating practices but do not accurately define what makes a Fluke anchor distinctive. For example, while some anchors may operate effectively in muddy bottoms, the Fluke anchor's defining feature is its shape rather than the type of vegetation it performs best in. Similarly, the size of an anchor does not directly correlate to its effectiveness; larger anchors are not limited to Fluke styles and often are designed for specific vessel sizes or conditions. The mention of weight being ideal for river use does not emphasize the unique shape that is crucial to the Fluke anchor's performance.