If you have only just started Spearfishing, you may not know that there is a difference in masks that someone should use for spearfishing, free diving and SCUBA diving. Of course, they can be interchanged at the beginning, but once you start getting serious with Spearfishing, you need a mask that is designed for it. In general, they are just smaller than a standard snorkeling or SCUBA diving mask. The reasoning behind this is that you need to be able to equalize quickly and regularly, and by having a larger mask there is more air inside, making it harder to do so.
When you are spearfishing you will vary the depth underwater very quickly (as a pose to SCUBA diving), which means that you need to be able to adjust your ear canals just as quickly. If you can’t do this, then you have to waste time trying to get it done before you continue moving, which wastes oxygen and could mean you miss that big fish just near you! If you keep swimming without equalizing correctly you are guaranteed to do some damage and regret it the next day!
Some spearfishing masks are designed with reflective glass, so that when you look at someone who is wearing one you can’t see their eyes. It has been a common theory for many years that some fish get easily spooked by divers if they can see their eyes. As a result, the reflective mask came out. You can also get masks that are designed to limit the bright light from the sun (mainly when you look directly up) and that can help you see better in caves. It is very difficult to do this with a normal mask as it can take up to a minute for your eyes to adjust, and by then your fish will have swum away! Of course, for many people a standard mask will be fine, but once you start diving deeper than 10 metres you should look at upgrading.