Can a Boat Made of Concrete Float?

*This post may contain affiliate links. As an Amazon Associate we earn from qualifying purchases.

Remember how in your childhood you were often hit with different kinds of questions that you would randomly think of? Some of the questions would seem quite weird, but would even manage to put many adults’ brains to the test as well. 

Speaking of things that piqued children’s curiosity, do you remember how you would have this question about how a nail sinks in water but a ship made of iron floats? 

That certainly sparked a lot of curiosity back in the day but the answer is virtually identical to the answer to whether a concrete boat floats or not. 

It always used to kindle amazement and amusement as to how this question or answer made any sense. It was a moment of equal amusement when we were told of how simple the reason was that some objects of the same weight and material would sink while others would float. 

The amount of liquid displaced by the object placed in it must be more than the volume of the object to make the object float. This is the reason why a nail sinks, but a ship made of iron travels across the oceans without sinking.

Ok so we obviously know that a metal ship will float but the question still remains will a ship made of concrete or any other material float as well? 

Surprisingly a boat that is made of concrete will actually float! As long as the boat is designed properly it will still float even if the hull is made of concrete. 

So now that we have established that a concrete boat can actually float there are a couple of other questions that you are probably wondering about. 

Related Post  Will A Boat Fit In Your Garage? Here’s How To Tell

Does the density of the material of which the ship is made affect the floating of the ship in any way? What exactly can ships be made of? 

That is too many questions to answer at once so we will try to do it one by one. 

The last question is really quite interesting. What is the range of materials that you can use to make a ship? Well, truthfully this list varies a lot. 

You can use almost anything and everything to make a boat. When we say anything and everything we mean anything and everything. 

Starting with wood and iron, you can even make a boat out of concrete and other incredibly heavy materials. Yes! This may seem impossible, but once you understand the principle mentioned above you can then understand how it’s actually possible for a concrete boat to float.

In this article we will look at how exactly a boat made of concrete even functions and whether it uses the same principles as that of one built from iron or not? So buckle up and read along!

Is Concrete a Buoyant Material?

Before going into details of if the material used in making a boat is buoyant or not, let us first understand what is buoyancy. 

Now, this is not a Science class going on, so let’s just go for a simple approach here. 

If you put an object in a liquid (water) and it floats in the liquid, then we consider that object to be buoyant. This ability to float is therefore called buoyancy.

But is concrete a buoyant material? 

As far as a common man is concerned, it certainly seems like concrete would not be able to float. It is hence not a buoyant material. Concrete is usually not considered to be a buoyant material and you can see this for yourself by dropping a chunk of it into your bathtub or a local lake. 

Related Post  Why are Boat Fridges So Expensive?

The crown of the king that was presented to Archimedes to measure the volume of gold in it, was of quite an irregular shape but concrete blocks are fairly regular in shape and hence are easier to experiment with. 

You can see for yourself how a piece of concrete sinks into the water and quite quickly at that! 

But how then does a ship made up of concrete float so effortlessly? 

That is the thing about science. It poses questions, makes you think, and then serves you the answer too. Everything we see all around us is, after all, a part of Science. 

Anyway, come on then, let’s see how a ship made of concrete manages to float in water. 

How does a boat made of concrete float?

We just saw that a block of concrete would not be able to float, and is hence declared as not a buoyant material but at the same time, we claim that a boat made of concrete can however float. How can an object made of a substance that is non-buoyant, float on the surface of the water?! 

It may sound bizarre, but let’s see why it is not.

Well, this is similar to the nail question we mentioned at the beginning of the article. The nail, when put in water, displaces water less than its volume and hence sinks. However, a ship which is made of iron is far bigger than a nail, but has a lot of space inside it left purposefully. This makes the ship displace a volume of water that is more than that of its volume as a result of which the ship floats on water. 

Similarly, a block of concrete has a lot more volume than that of a boat made out of it. The amount of water displaced by the block is way less than its volume and hence fails to provide it with a buoyant force, causing it to sink and being labelled as a non-buoyant material.

Related Post  Will A Boat Start In Gear?

The main principle that is being used here is the definition of density. 

It is described as the measure of the amount of matter present in an object. It is the amount of matter that could be squeezed into the given space within the object and hence points towards the compactness of the object. 

In much more scientific and technical terms (as if that wasn’t technical enough) the density of an object is described as the mass per unit volume of the material. The comparison of densities of different materials and substances is what is being used here as logical explanations.

So despite that fact that concrete is quite dense and is not buoyant by itself when it is shaped in such a way that allows the concrete boat to displace a larger volume of water than what the concrete boat is thereby allowing the concrete boat to float! 

Crazy isn’t it! 


Science is fascinating don’t you think?! It is how the universe is working and growing every minute and second of every day. It has a certain sense of arbitrariness attached to it as it is filled with exceptions and different kinds of explanations for different things. However, it still has this attraction of excavating the secrets of the universe and that is what has lured, is luring, and will keep luring people with the capability to think towards it!

Matthew Robbs

I love the outdoors and especially spending time with my family. Whether on a boat or at the beach, my happy place is near the water.

Recent Posts