The camera/housing lens or front LCD is fogging. This generally occurs when the camera is warmer than a cool or humid environment and is especially common when the camera is being used in water. 

How to fix it?

The fogging resolves when the camera and environment are equalized -- similar to how your breath stops fogging your car's windshield once the heater warms up. Fogging does not damage the camera in any way.

If you are using the camera with housing in an environment where the lens is fogging up, you can use Anti-Fog Inserts designed specifically to alleviate this issue. The anti-fog inserts help prevent your camera's housing lens from fogging, even in cold temperatures/humid environments.

There are some additional steps that you can take to stop or minimize the fogging:

①：If you are using the camera in conditions where waterproofing is not needed or where high wind noise is not an issue, then you should open the back door of the housing. Using the open back door for the housing will ensure that the temperature inside and outside of the housing is equal. 

②：Turn off any settings that you do not need (Wi-Fi, Voice control, etc.) as this helps the camera run cooler.

③：Keep the camera as cool as possible if you'll be introducing to a colder environment (ex: if you're going diving, keep the camera in the dive boat's bucket of freshwater for rinsing gear until it's time to use it). If you're at the beach, keep the camera in the shade and not out in the sun. 

④：Ensure that when you are opening the battery door, you have dry hands and that the camera is dry.