A fish has to be right on top of its food for feel to be of any importance, and at best, sight under water is limit to a few yards. The density of water is such that it transmits sound five times farther than the air above. Scent ranks first because it ranges great distances in water. Sharks as an example can detect the scent of blood from as far as a mile from the source. This is one way moving water or currents come into play.
Currents carry scent great distances, enabling game fish to accurately home on their source of food.
Thus, it behooves the sports angler to fish during periods when there is sufficient water movement to create these chum lines. Now consider how currents intertwine with tides. The more tide changes within a 24 hour period, the more water movement. The degree of water movement links directly to the time period between two tides and the height of the water on the tide stand as compared to the height of the water immediate following tide stand. Tides are controlled by the moon's position in relation to the sun and earth.