To gain an advantage, we peel spruce poles, lash them together, and sink them with rocks. The poles are crosswise on the creek bottom. When the fish swim with or against the current, they show up clearly as they swim over the light colored poles. A white sheet or cloth held on the bottom by rocks serves the same purpose. However, if you spear too many holes in your mom's sheets, she will not be too happy.
Wooden poles are better in that regard.
Years ago, before nylon nets were available, upriver people speared salmon from canoes. If king salmon are speared in the right place, just behind the brain, they quiver and die easily. Accuracy is important. The challenge It is exciting to spear fish, but our first efforts are usually frustrating. There is a science principle that must be understood before we can successfully spear fish.