How Do Boats Float? A Beginners Guide

There will be very few people living on this earth who are not familiar with a boat. Because we live in a place called planet earth, which is almost mostly filled with water.

Even many of us might also think that what would be the reason behind the floating of a boat on the water while we are cruising on the sea or just kayaking on the lake.

From the long history of human being, we can see that boat has been using since the very first of the civilization. But as days have passed and humans came to know more about science, then the revolution begins on a different level, for example, ships like multi-storied cruising ships, cargo ships, etc.

What is a Boat?

A boat is a vehicle that has its mobility only in water like a sea, a lake, or a river. It can move through the water using energy like winds, waves, etc. On the other hand, it can also move using the energy generated by any engine. A boat can be found in two types. 

One is the normal one that we see moving through partially above the water level. Another one is the submarine that goes deep down inside the water level.  The second one is mostly used for military purposes, while the first one is used for commercial purposes.

Why Do Boat Floats?

Here are the reasons why boats float:


No boat in this entire world doesn't float other than the cracked or broken one. The concept of floating is a bit complex because if you want to understand it, then you need to know about buoyancy.

In simple words, any boat that floats in the water mainly because the amount of water displaced by the boat creates an upward pressure. Until the upward pressure of the water is more than the downward force or gravitational force.


Usually, boats are made in such a way that they can have stability through rough waves in the sea or in the rivers. But that doesn't mean that it will never lose its stability and tip over.

When you are on a small boat, you will notice that it will lean to one side very easily as you move to the other side of the boat. On the other hand, you will see that it has no effect when you are on a large ferry.

Design of the Boat

Designs of large steel made a boat like a ferry, cargo ships, and cruise ships are in such a way that, in every way it will make sure that it is displacing enough water to keep it stable by the upward pressure of the displaced water.

Density Level of the Boat

Different boats are made with different materials. Usually, larger boats like ships are made with heavy material. These materials are denser compared to water.  In the case of the larger boat, the hull must have an average density which is lower than the density of water.

Without achieving it, the ship won't be able to float at all. When there is a larger hull, it reduces the average density of the boat. A larger hull keeps a vast amount of air, which helps the boat to float.

Following the Plimsoll Mark

Not every water area has the same density, which creates a huge impact on the floating of the ship. Less dense freshwater will not allow any larger boat like ships to float very high from the surface level. On the other hand, saltier water has more density, which enables the boat to float quite high. 

If the shipping driver doesn’t follow or check the Plimsoll Mark, then the ship has a high probability of sinking in the sea. Usually, the captain takes note of the seaways and fixes the loading limit of the ship.

Archimedes Theory

A renown scientist known as Archimedes came up with the idea that whenever an object is in the water, it feels an upward pressure. And the pressure is equal to the amount of the water displaced by that specific object.

For example: If a boat weights 500 kg and it is on the water surface, then only it displaces the same amount of water from that place. The ship doesn't submerge because it is made in such a shape, which allows the exact amount of water from its place before it submerges.

Mainly the larger and smaller boat doesn't sink because the average density of the air and steel of the boat is not more than the average density of water. The same boat that feels heavier in the solid ground will feel the lesser weight because of this upward force of the water.

A Boat Does Not Turn Upside Down 

Small boats may become unstable very easily, while the bigger ones are rarely. The main reason behind this is the center of gravity, which allows it to act like that.

As long as you are not sitting on a small boat and moving from one side to another, then it will rotate from one side to another. Positive buoyancy allows it to do that, which requires very little force. 

In the case of larger boats like ships, the engines are positioned at a very lower level.  Or in other words, it is beneath the water surface level, and it gives the ship a center of gravity. This is the main reason behind the stability.

Also, another main reason is that every large ship has a huge vertical board at the lower outer part of the ship, which prevents the boat from rolling from one side to another.


From ~10,000 BCE to this year, humans have been using the boat as a part of their life. Already you have a little bit of idea how a boat floats and basically what is the main reason behind it.

You can share this knowledge with other people like children or anyone who doesn’t know about it.  Now, you can educate people about the background scenario of a floating boat.

Last Updated on March 9, 2021