Two high and two low tides in a lunar day of 24 hours and 50 minutes

Background

Tides are very long-period waves that move through the oceans in response to the forces exerted by the moon and sun.
The difference in height between the high tide and the low tide is called the tidal range.
The incoming tide along the coast is called a flood current and the outgoing tide an ebb current; the weakest currents, between the two, are called slack water.
Most coastal areas experience two high tides and two low tides every day, because the Earth rotates through two tidal bulges in one lunar day, and a lunar day is 24 hours and 50 minutes.
High tides occur 12 hours and 25 minutes apart, and it takes six hours and 12.5 minutes for the water at the shore to go from high to low.
When the sun, moon and Earth are in alignment, at the time of the new or full moon, the solar tide adds to the lunar tide and the result is commonly called spring tides.
One week later, when the sun and moon are at right angles to each other, the solar tide partly cancels the lunar tide and produces moderate tides known as neap tides.
During each lunar month two sets of spring tides and two sets of neap tides occur.