Low slack occurs at the transition from ___________ to __________.

Low slack specifically occurs at the transition from an ebbing tide to a flooding tide. This is the moment when the water level reaches its lowest point just before the flow of water changes direction. During low slack, the water is essentially at rest, which means that the current is minimal and the tidal influence is changing from one phase to another.

Understanding this transition is essential for navigation, as it signals the point where tidal movements begin to shift; knowing when low slack occurs can greatly affect sailing and boating operations. It is a critical time when mariners can expect calmer waters, making it safer and easier to navigate in potentially turbulent tidal conditions.

In contrast, other choices describe aspects of tidal flow but do not accurately define low slack. For instance, transitioning from a flooding tide to an ebbing tide refers to the period after low slack has passed, while the transition from slow to fast current or vice versa speaks to varying speeds of water movement, rather than the high or low points of the tide itself.