The first thing is to be in the right place at the right time with the appropriate gear. It is important that you find an area with clear water and ample fish.
It is also important that you choose a stick with a sharp pointed end as your spear. Now you need to dive in the water and let your body weight push you towards the bottom. You need to move as little as possible, which means kicking your legs is the last thing which should be on your mind as this will frighten the fish away.
Once you have reached the bottom, you now need to creep slowly in the direction of the fish. You can firmly hold the spear in your throwing arm and crawl by pushing with your free hand. If you need to kick your legs, do it very slowly. It is preferred that you hide behind rocks so that you are not visible to the fish.
Once the distance between you and the fish is enough for the spear to pierce through your prey, you need to extend your arm and release the spear smoothly while aiming at the head of the fish.
Once you have hit your target, you need to immediately kick yourself towards the fish to grab it or the spear. You then need to swim up towards the surface and walk out of the water with the fish still impaled on the spear.
You can spear the fish from the surface, in the same way, however, you have to walk to the area with maximum fish and then throw the spear once you have located your target.