Why do ships tied to docks experience two high tides and two low tides each day?

Ships tied to docks experience two high tides and two low tides each day due to the gravitational pull of the moon and sun on Earth's oceans, creating bulges of water. As the Earth rotates, these bulges move, resulting in the rise and fall of water levels, known as tides. Typically, most coastal areas experience a semi-diurnal tide cycle, which means there are two high tides and two low tides approximately every 24 hours. This rhythmic movement affects the water levels at the docks, causing ships to rise and fall with the tides.