What hazard does a large diameter submerged object require in terms of marking?

A large diameter submerged object poses a significant hazard to navigation, making it essential to mark the danger clearly and effectively. The appropriate marking for such an object is a wreck mark buoy or a special mark buoy.

A wreck mark buoy is specifically designed to indicate the presence of a wreck or submerged object that could be dangerous to vessels. This type of buoy typically has a specific color and shape that sailors recognize as signaling a hazard, thereby alerting mariners to exercise caution in the area. Furthermore, a special mark buoy can also be used for this purpose, as it indicates a feature or area that requires specific attention, which in this case highlights the submerged danger.

This distinction is crucial since the presence of a submerged object can lead to grounding or collision, and proper marking helps ensure the safety of navigation by warning mariners about potential hazards that are not visible from the surface. The other choices would not adequately address the need to communicate the specific hazard presented by a submerged object in the water, as they are meant for different navigational purposes.