What device is effective for protecting an unconscious victim while crossing the surf zone?

The best choice for protecting an unconscious victim while crossing the surf zone is a rescue buoy. This device is specifically designed to provide flotation and can help keep an unconscious victim's head above water, which is crucial when navigating through potentially turbulent surf conditions. The buoy also serves as a visible marker, allowing other rescuers or bystanders to easily identify the location of the rescue.

A snorkel, while useful for underwater breathing, does not provide any flotation and does not protect the victim's airway. In surf conditions, the priority is to ensure the unconscious victim remains afloat and their breathing is not obstructed, making the snorkel an ineffective option. Fins may assist in swimming but do not directly contribute to the safety of the unconscious individual. A pocket mask is valuable for providing rescue breaths but does not offer flotation support, which is essential when moving through waves.

Thus, using a rescue buoy is the most appropriate and effective method in this scenario, as it addresses both flotation and visibility for a surfer in distress.