This does not mean that all the underwater cameras that you see are made equal, and it also does not mean that fishermen can rely on getting a good one without learning anything about them. Many units are either too cheap or they are simply too simple to be useful or they are not well suited to the extreme weather conditions that are associated with ice fishing. So, what exactly should you look out for?
The fist thing that you should look out for would be insulation of some sort for the unit and especially its battery. The LiPo batteries that get too cold can have water condense inside them and this could cause them to short out and catch fire, so it is very important that you keep them reasonably warm.
Fortunately, they create their own heat when they are in use, so as long as the camera comes with insulation around the battery, it will work properly at cold temperatures.
Second, the line and camera must be insulated with cold-tolerant materials that will not become hard when exposed below freezing temperatures. You would need to avoid natural rubber at all cost, and all of the waterproofing on the unit needs to be made of silicone or something similar to that material.
Third, the camera needs to have a large camera aperture and large pixel resolution. You should beware, too, that water blocks out infrared light effectively, and so infrared cameras will not be able to see as far as those that focus on visible light, especially in the blue end of the color spectrum.
Finally, the camera would need to have an IP68 rating. What this means is that the camera has been developed specifically to be submerged in the water below one meter (this is a little more than a yard) and it will not fail you once it is immersed.