It's not steam it's condensation and yes I get it too. There are a number of possible ways to solve this issue.

The one I use is to put silica gel (the packs of stuff that come in the box with a pair of new shoes) in the housing and seal it up a good 24hr before i'm going to use it in the water. What the silica gel does is remove the humidity from the air so when you get a temperature change within the housing there isn't enough moisture level in the air to get condensation.

Another option is to seal the gopro in the housing in your freezer in front of the cool air vent, or in front of the aircon vent in your car with it on full ball. Air conditioned air is dehumidified and cars and frost free fridges don't have humidifiers added such as a household AC system may.

It's a bit of a pain in the arse but those are some work arounds to try.