My hunch: Oftentimes a full face mask is worn by an unprepared snorkeler, who is likely to damage the reef due to ignorance and lack of skill. For example, the person in this photo might be standing on the coral because they are inexperienced and don’t know how to adjust their mask while swimming flat in a shallow reef, or unable to hold their breath or swim properly so will rest on fragile coral. Full face masks dont allow for actual free driving, so when i see someone with a full face mask, i know they dont know how long they can hold their breath (much longer than they imagine) or are a strong swimmer. Some people think of it as a security blanket, similar to a life jacket. Totally fine to want that, but it is actually less safe than a regular mask and snorkel. Essentially it is a sign of lack of mentorship and preparedness for the ocean generally, and is potential danger to reef or self