On these images we see the low tide and the high tide.
Step-by-step explanation:
On the two images we have the same place but with two contrasting views. On the picture on the left we see that the water level is higher and the boat is floating, while on the picture on the right we can see that the water level is lower and the boat is on dry land. This is actually a representation of low tide and high tide.
The high tide occurs twice in 24 hours, on roughly 12 hours. It is the process when the water level rises and comes further toward the land. The low tide also occurs twice in 24 hours, and also on every 12 hours. It is the process of retraction of the water toward the sea. These processes occur because of the gravitational pull of the Moon (primarily), and to a lesser extent of the Sun as well.