Final answer:
Snorkeling is appropriate for searching the shallows with good visibility for the lost mask, being efficient and practical in such conditions. Deeper or more complex searches would involve scuba considerations like buoyancy and gas pressures.
Step-by-step explanation:
Given that the search area for the lost mask has excellent visibility and is no deeper than 10 meters/30 feet over a sand bottom, it would be appropriate to search from the surface snorkeling. Snorkeling allows for efficient scanning of large areas when visibility is high and depths are shallow. Complementing this with organized search patterns would increase the likelihood of locating the mask.
Scuba diving techniques and considerations such as buoyancy, pressure equalization, and the amount of time spent underwater are crucial factors taught to divers to handle the risks associated with pressurized gases in the body, and while these are less of a concern when snorkeling at shallow depths, they do become relevant if the search were to be extended deeper and require diving with scuba gear.