As long as they are working properly. The problem is that the valves can fail (or not be properly designed in the first place), and then they become dangerous.

As long as they are working properly. The problem is that the valves can fail (or not be properly designed in the first place), and then they become dangerous. https://www.ktvu.com/news/recent-snorkel-deaths-prompts-investigation-into-full-faced-snorkel-masks https://www.ktvu.com/news/recent-snorkel-deaths-prompts-inve...