Where I live, the tide determines whether I walk on the beach with sand between my toes or high atop cliffs following the shoreline. At high water, the tide builds to 6 feet with waves crashing against the cliffs and the beach under water. At low water or low tide, waves ebb all the way back to zero feet, exposing the sand and revealing tide pools in a rock plate that juts out into the bay.
The waves ebb and flow in much the same way every day. Two low tides in a 24 hour period. Two high tides. Waves come in an hour later today than they did yesterday. Waves go out. The parameters remain the same. The difference is the interaction or relationship between our moon, sun and the planets we travel with through space.
You can physically feel the difference in the energy created at low tide compared to high water. As the tide builds and waves begin crashing against the cliffs, the energy all along East Cliff builds right along with it. At low water, the energy wanes as waves gently lap and then altogether disappear.
Low tide holds the same sort of energy as do scenes of reflection before a story begins and then again after a trauma or a crisis, a major turning point -- more introspective, contemplative scenes without much external conflict and where the protagonist is not feeling threatened = below the line scenes.
High tide is like high action, movement, noise, chaos in the middle of a story where anything and everything can happen and does and then again in the build-up to the climax -- all above the line scenes on the Plot Planner. (For examples of working Plot Planners and The Plot Whisperer Workbook: Step-by-Step Exercises to Help You Create Compelling Stories has all the planners and trackers you need -- one workbook per story.)