Since the "Dawn of Man", people have been using Casting nets to gather their "catch" from their local waters and provide their families with nutritious fish.
Literally, cavemen and women have left behind drawings of people using and throwing nets to provide for their loved ones.
The nets, themselves, haven't changed much in all these years. Mostly round (in order to make it easier to open up the net as it was cast and was about to hit the water). Stones, or weights were added to help it sink and capture it's prey.
Then came the varying lengths to the net. This obviously was so that the fisherman could gather more fish at any one time, but rest assured that you really had to be strong to haul in the long nets, if they caught any amount of fish at all.
The throwing (casting) of these nets is truly an art form. It is not something one can master easily and will take some time for each fisherman to be able to determine their own personal, effective way that will work for them.
Essentially though (and this is ONLY a basic, basic explanation, thousands of books and videos are available, online, to learn this skill), the net is held high and straight to make sure there are no kinks in the netting, itself. The caster, then lays the net over their shoulder and separates one edge of their net from the opposite side of the net.
Holding the casting rope, the upper end of the net and the opposing edge, the thrower slings the net outward in a circular motion and hopefully, done properly, the net opens as it lands on the water's top.
When it's sunk sufficiently, the caster starts by retrieving the casting line, which will draw the net back to the fisherman (and with any luck, it will be filled with fish).
Net fishing can be accomplished from a boat, from the shore or by wading in the water. Either venue, you choose, can be as fruitfull.
Net casting is normally used for catching bait fish, or for catching smaller fish that won't bite a baited hook. Sportfisherman, love to use this method during tournaments for catching their "live bait" that will help them catch those "big billfish".
The only drag on this method is that it is done in the wee hours of the morning when most tournament fishermen don't choose to get up, so an alternative for them is to spot the entrepreneurs "bait boats", on the way out the inlet and purchase their "catch" from them at really high prices. Etiher way will work!
Islanders, in the Bahamas and Micro & Polynesia and such still use this effective method of catching fresh fish quickly to provide food for their families.
It is still an artform handed down from father to son. And in this day and time even the daughters are included in this skilled learning process. In fact, in South Florida at most of the "big time billfishing tournaments", one of the highest paid "entrepreneur bait boats" is owned and operated by a teenage girl.