How to prevent fogging in Olympus TG-5 / TG-6 housings?

Usually this happens because you had some water enter the housing, either from a minor leak or because of dripping inside the housing while handling it / opening it.

If some water is trapped within the little cracks and buttons, it will vaporize and fog up the housing.

The best way to prevent it is by thoroughly drying the inside of the housing with a an air blowing device or leave it in front of a fan for a day or two. While drying it work all the buttons to make sure any moisture comes out.

Another cause would be if you used the camera in water, without the case, then put it in the case while there’s still some moisture on the camera. That will likely cause fog as well. The camera should be 100% dry before putting it in the case. You can use the fan method to dry the camera as well.

If after this the housing still fogs up, there may be a minor leak letting in more water in the housing. You can rinse it with warm water (closed!) to try to get rid of salt residue which may cause minor leaks in the controls, then dry it up again and check if the problem is solved.