On Amazon as of May.2023:
www.amazon.com/dp/B0BWFXB2BM?...
The full face snorkel mask is a relatively new invention that has grown in popularity in recent years. Unlike traditional snorkel masks, it covers the entire face and allows the wearer to breathe naturally through the mouth and nose. However, in certain situations, CO2 can build up in the mask, which can lead to pendulum breathing and ultimately suffocation.
Pendulum breathing occurs when the body takes in too much CO2 and the breathing reflex is suppressed. As a result, the wearer is not breathing deeply enough and may experience oxygen starvation. This can especially occur in snorkelers and divers who are physically strenuous or under stress.
To minimize the risk of CO2 build-up and pendulum breathing, it is important to choose a quality full face snorkel mask and use it carefully. It is also advisable to take regular breaks and take deep breaths.
Overall, the full face snorkel mask can provide a fun and convenient way to explore the underwater world, but it's important to be aware of the potential risks of an improperly constructed mask.