Difference Between Sea and Ocean

Sea and ocean are both water bodies yet they share many differences and similarities among them. We may think that both just contain water in them and what might be the possible difference, but still, there are major differences, facts, and points about both that separate them from each other.

What is an Ocean?

Oceans are water bodies that incorporate more than 70% of the earth’s surface. There are five oceans in the world. Namely the Pacific Ocean, Indian Ocean, Arctic Ocean, Atlantic Ocean, and the Southern Ocean. Oceanography or oceanology is the study of physical and biological characteristics and features of the ocean and its organisms. The ocean water is alkaline and makes them unfit for drinking. The rivers have carried the minerals, rocks, and soil from the land and brought it to the ocean, which makes the ocean salty. The minerals are mostly sodium and chloride which makes up the common salt. 

It can be seen that oceans are not bordered or separated by any landmarks. Hence, all the oceans combine to make a single large water body on the earth’s surface. To our convenience, we have grouped the ocean based on its location. The Arctic ocean named after the arctic region likewise the Indian ocean named after India which is approximate to the ocean. 

It is observed that the oceans that approximate the north and the south poles are less saline in nature than the oceans which are situated more towards the equator. This is because the tropical region receives more sunlight than the poles. So the water in those regions evaporates faster and concentrates on the water. 

The color of the ocean is mostly blue as perceived. It would be fascinating as we have learned that water does not have any color but yet we perceive oceans and seas in blue color. This is because the sunlight that is emitted on the water bodies have different wavelengths of light. The red part of the sunlight is absorbed resulting in the blue color of the light being reflected back to the atmosphere.


Tides are the rising and falling of water in the ocean and other water bodies. It is mainly seen in large water bodies like oceans and seas. The tides are caused due to the exertion of the moon’s gravity on earth. Since the moon revolves around the earth, it exerts a gravitational pull towards the earth’s surface. Since the earth rotates around its axis, the side facing the moon experiences a high tide which is a bulge in the ocean. Which keeps changing as the earth keeps rotating. On the day of a full moon and new moon, the earth and sun and moon align with one another causing a maximum bulge in the ocean. These are called High Tides. And the area opposite to the earth’s surface will experience low tides. Hence, oceans keep experiencing high tides and low tides frequently throughout the time of rotation and revolution.


Waves are the motion of water in oceans caused by the wind. The wind shifts some of the energy to the water molecules when it moves over the surface of the ocean. This causes water to move in oceans and seas. It may seem that waves are moving in a horizontal direction, but they just move vertically.

What is a Sea?

Seas are the water bodies which are smaller than the ocean, and partially landlocked on either of the sides. There are few seas that are fully landlocked saltwater lakes like the Caspian Sea or the Dead Sea which is technically a lake but still called Sea. There are also seas that contain freshwater, one example is the Sea of Galilee. 

The seas also have similar features as that of the oceans. It also consists of waves, tides, and water currents. Sea currents are the flow of the water within the sea which travel different directions based on the geography, temperature, wind, and ocean currents. The salinity of the sea is measured with the unit of parts per thousand (%), the normal seawater is very alkaline. It normally ranges about 35%, but the seas like the Mediterranean Sea is about 38%. In landlocked saltwater lakes, the density of the salt in water is too high ranging about 300% given an example of the dead sea. 

A water cycle is the main event that takes place in almost all the water bodies. The water from the seas, oceans, lakes and other water bodies evaporate into the sky forming clouds. The clouds become denser and start cooling down eventually, causing the water to come back to the earth in the form of rain. This event is very important as rainwater plays a major role in plant growth, agriculture and many other events. 


Coasts are an important feature of seas. It is the point where the land meets the water body. The coastline is a total length of the area that surrounds the land, particularly when we look into the geography of a land. Beaches are the area covered with sand and rocks near the sea where people may come to relax for a vacation. 

Creatures of the Sea

Marine life is extremely important for the survival of the biosphere, as the carbon cycle is regulated by the creatures of the sea and ocean. The range of creatures living in the sea is abundant. It can start from small phytoplankton to large whales. Here marine life is divided into coastal habitats and open water habitats. The coastal habitats range from the coastline of seawater and may go up to the continental shelf whereas the open water inhabitants live in the center of the sea or ocean.

Phytoplanktons produce almost half of the world’s oxygen and are the primary producers of the marine ecosystem.

Difference Between Ocean and Sea



The ocean is an enormous, continuous water body that contains almost 70% of the earth’s water and frequently does not have any borders.

Sea is a comparatively smaller water body that is either partially landlocked and has water quantity lesser than the ocean. 

The depth of the ocean is much greater than the sea. The deepest ocean is the pacific ocean with a depth of around 10924 meters.

The depth of the sea is lesser than the ocean mostly due to the land enclosing seawater. The deepest sea is the Carribean sea with a depth of around 6946 meters.

The area of the ocean is greater than that of the sea. The largest ocean i.e the pacific ocean covers an area of  60million square miles.

The area of the sea is smaller than that of the ocean. The largest sea i.e the Meditteranean sea covers an area of about 1.14million square miles.

Oceans have less marine life than sea as sunlight cannot penetrate deeper into the water and photosynthesis does not take place.

Sea has larger marine life as compared to oceans as it is enclosed by land and the water is shallow, the sunlight penetrates and causes photosynthesis to take place.

Marine life in the ocean is different from the sea, usually those creatures which need less sunlight like phytoplanktons, whales and other creatures.

Marine life in the sea consists of creatures that are more dependent on sunlight, also creatures that can live in both land and water like lobsters, crabs, etc.

Oceans do not have other oceans inside them like seas. Oceans are divided based on the area which they are approximated to but in total are connected and are called the World Ocean.

Few seas enclose other seas inside them. For example, the Mediterranean Sea also called the Great sea encloses the Ionian sea, Libyan Sea, Gulf of Lion, Balearic Sea, Sea of Sicily and the Ligurian Sea and many other seas.