What characterizes a full-face mask for contaminated water diving?

A full-face mask for contaminated water diving is characterized by offering comprehensive facial protection. This type of mask not only covers the eyes and nose but also encases the entire face, including the mouth, which is critical in environments where contaminants might be present in the water. By providing this all-encompassing coverage, it serves to protect divers from harmful substances, ensuring that the eyes, mouth, and airways are not exposed to potentially dangerous elements.

Additionally, full-face masks are designed to accommodate various breathing methods – including the ability to breathe normally through both the nose and mouth, thus enhancing the diver's comfort and safety in hazardous conditions. The comprehensive design also allows for the integration of communication systems, making it easier for divers to communicate while safely submerged.

The other aspects mentioned in the incorrect options do not accurately describe the nature and purpose of a full-face mask in contaminated water diving. While full-face masks are generally more substantial than traditional masks, they offer significant advantages in protection and functionality that are more critical than weight alone.