Diurnal vs. semi-diurnal tides
Diurnal or daily tides - have a single high tide & a single low tide per tidal day
Semidiurnal or semidaily tides - have two high tides & two low tides of approximately equal height each tidal day
- Semidiurnal tides may have daily inequity, where successive high tides have different heights
- Semidiurnal tides often easy to predict because high (or low) tides occur a consistent length of time after the moon has passed overhead