Explanation:
Water-related natural calamities are events that are caused by the presence or movement of water. One such type of natural calamity is a flood.

Flood:
- A flood is an overflow of water onto normally dry land. It occurs when there is an excessive amount of water in a river, lake, or any other body of water, causing it to spill over onto the surrounding areas.
- Floods can be caused by various factors such as heavy rainfall, melting snow, dam failure, or even tsunamis.
- When a flood occurs, it can lead to the submergence of houses, buildings, and agricultural fields, resulting in the displacement of people and destruction of property.
- Floods can also cause damage to infrastructure such as roads, bridges, and power lines, disrupting normal life and communication.
- The impact of a flood can be severe, leading to loss of life, damage to crops, contamination of water sources, and the spread of waterborne diseases.
- Floods can occur in both coastal and inland areas, and their severity can vary from mild to catastrophic.

Other options and their explanations:
- Earthquake: An earthquake is a sudden shaking or trembling of the ground caused by the movement of tectonic plates beneath the Earth's surface. It is not directly related to water.
- Landslide: A landslide is the mass movement of rock, soil, or debris down a slope. While water can contribute to landslides by saturating the soil, it is not the direct cause of landslides.
- Cyclone: A cyclone is a large-scale atmospheric disturbance characterized by low-pressure centers and strong winds. While cyclones can cause heavy rainfall and storm surges, they are not caused by water itself.

Therefore, the correct answer is option D, flood, as it is a natural calamity caused by the presence of excessive water.