High tides help in navigation as they raise the water level close to the shores. This helps the ships to s arrive at the harbour more easily.The high tides also help in fishing. Many more fishes come closure to the shore during high tides. This enables fishermen to get a plentiful catch. The-rise and fall of water due to tides is being used to generate electricity in some places.

Tsunami is a Japanese word meaning 'harbour waves' as the harbours get destroyed whenever there is tsunami. An earthquake, volcanic eruption or underwater landslide might trigger huge ocean waves called tsunami.
Effects :
(i) These waves travel at a speed of 700 km per hour and cause damage to the coastal areas.
(ii) The areas near the coast get submerged and it leads to earthquake.

(i) During the full moon and new moon days, the sun, the moon and the earth are in the same line and the tides are highest. These tides are called spring tides.
(ii) When the moon is in its first and last quarter, the ocean waters get drawn in diagonally opposite directions by the gravitational pull of sun and earth, resulting in low tides. These tides are called neap tides.

Rhythmic rise and fall of ocean water twice a day is called a tide.
There are two types of tides:
High tides: It is high tide when water covers much of the shore by rising to its highest level.
Low tides : It is low tide when water falls to its lowest level and recedes from the shore.

Differences between waves and tides are 

Tsunami is a Japanese word that means 'Harbour waves' as the harbours get destroyed whenever there is tsunami. An earthquake, a volcanic eruption or underwater landslides can shift large amounts of ocean water. As a result, a huge tidal wave called tsunami, that may be as high as 15 m, is formed.
The largest tsunami ever measured was 150 m high. These waves travel at a speed of more than 700 km per hour. The tsunami of 2004 caused widespread damage in the coastal areas of India. The Indira Point in the Andaman and Nicobar Islands got submerged after the tsunami.

When the water on the surface of the ocean rises and falls alternately, they are called waves. During a storm, the winds blowing at very high speed form huge waves. These may cause tremendous destruction. An earthquake, a volcanic eruption or underwater landslides can shift large amounts of ocean water. As a result, a huge tidal wave called tsunami, that may be as high as 15 m, is formed.

High tides are important for various reasons
(i) They raise the water level close to the shores. This helps the ships to arrive at the harbour more easily.
(ii) The high tides also help in fishing.
(iii) Many more fish come closer to the shore during the high tide. This enables fishermen to get a plentiful catch.
(iv) The rise and fall of water due to tides is being used to generate electricity in some places.

Ocean currents are streams of water flowing constantly on the ocean surface in definite directions which may be warm or cold.

The rhythmic rise and fall of ocean water twice in a day is called a tide. They are caused by strong gravitational pull exerted by the Sun and the Moon on the Earth's surface

The factors which affect the movement of ocean water are temperature, winds, gravitational pull of the Sun, the Earth and the Moon.

The falling of moisture on the Earth in the form of rain, snow, hail, sleet or mist is called precipitation.

No, only 3% is fresh water. Its 0.3% is available to us.

Due to the following reasons, some countries face water scarcity
• Some countries are rocky and arid.
• Some do not have much rainfall.
• Some are desert areas.
• Most of the water is polluted.
• Excessive use of water has depleted water resources.