Can a giant mushroom be used as a material to build watercraft or sailing ships?

Question

The basis for this question is the selected answer for Plausibility of Mushroom Buildings. Prototaxites and braket fungus are the likely candidates but I want to know if this type of fungis can float on water or not, so that it can be used to build a ship.

My question is not restricted to that fungus, it is just generally about the possibility to build ship with giant mushrooms. If simple giant mushrooms can do it and can be hard enough to withstand ocean waves, impacts and other nautical challenges in order to be viable as a ship then it's good enough.

Feel free to suggest new solutions or alternatives from any fungal or fungal-like organic material if prototaxites and braket fungus is not suitable to build ships with, as long its not the obvious trees and metals as materials.

Answer 1

Ships can be built out of teak, a wood that doesn’t float. So whether the fungus floats is not important.

It does need to have a measure of rigidity and strength to be used for constructing a hull or mast. I can’t see any info on the material strength of this extinct fungi. But, most fungi when dried become porous. I imagine it could be soaked in resin or a mixture of tar and pitch and that would make it kind of stiff and hard. Then it could be used for some type of watercraft or ship, depending on its strength.

Rigid but moderately strong materials could used for rivers and coastal crafts. And, for limited applications, it could be used for seawater craft. I liken the type of material to balsa wood. The explorer Thor Heyerdahl built his vessel out of balsa and sailed from South America to Polynesia.

Very rigid and strong materials could be used as a wood substitute and any kind of ship could be fabricated from it

Answer 2

A material doesn't have to be less dense than water to be viable for a hull. All ships sink if they take in water after all. If they were all made of materials less dense than water, at the very worst they would float poorly after taking in water and/or enough hull damage.

Ships float because the volume of water they displace is heavier than them. In a sense, the ship and its contents as a whole are less dense than water, even if the ship's structure is made of something denser than water. In layman terms, a ship's hull may be heavy, but it is hollow and the things filling it up (including air) are in average lighter than water.

That is not all, the hull needs a proper shape to make the most of the water pushing it upwards. I won't get into hydrodynamics here though.

Your hull must be strong enough to:

• Support its own weight and cargo;
• Keep its own shape under a lot of pressure.

We will probably never know the structural properties of prototaxites because they are extinct. But there is a company called The Living that is making bricks out of mycelium (the structural stuff of fungi):

If bioengineering can be used to make bricks, I don't see why it could not be used to make hull boards. We just have to tweak with the mycelium's structural properties until its tenacity, hardness, strength and maleability are close to that of wood.

In fact, if we ever manage that, fungal boats might become a thing. Fungi can be made to grow into arbitrary shapes much more easily than plants. They also feed on practically anything that has once been alive and don't require sunlight. Who knows, they might be cheaper and better than wood if we ever developed the technology.