When you are out spearing, proper freediving or spearfishing fins will make a huge difference in your performance. The most important aspect for such fins is that they have closed heels instead of just straps. This will transfer much more power from your legs into the blades than open heel fins do. Imagine it like running in well fitting sneakers versus running in thongs.
Spearfishing fins are also longer and more flexible than regular fins, thus creating greater propulsion in order to get you further with less effort.
There are several types of blades for spearfishing fins.
Polycarbonate blades are great for beginners, as they are lowest in price while being sturdy to last you a long time.