The shoreline is a moving boundary
A beach is not a fixed line on a map. Twice a day in many coastal places, the water changes where the land seems to end. That motion comes chiefly from the Moon’s gravity, with the Sun contributing too. Local geography, weather and coastline shape determine how the tide looks in any particular place.
Look for the high-water mark
Wrack lines—thin bands of seaweed, shells and driftwood—often record where recent waves have reached. They are clues, not precise tide charts. Storm surge and onshore winds can move water much higher than predicted.
Check before you go
If you explore rock pools or walk a tidal causeway, always consult official local tide tables and weather warnings. Leave yourself more time than you think you need, and never treat a visual guess as a safety forecast.
Take home a habit
Visit the same place at different tide states, notice which rocks emerge, where birds forage, and how the sound changes. The coast becomes more interesting when it is familiar.