@MiiaBestWaifu I get where you are coming from as I have seen some Isekai's where the MC saw a "How it's Made" episode once and was able to fully reproduce a battle ship. That shit
is ridiculous.
But on the other hand the concept is not that far off from plausible, (given enough time for testing).
You don't need a blueprint of every nut and bolt, and every inch and curve memorized to describe an idea. Concepts can be vague and still get across, specifics usually come later. The more specifics you have the less time needed for trial and error.
A water wheel is a novel idea that would have been useful by itself. Attaching a water wheel to a regular ship would provide valuable propulsion in your desired direction even when the wind or current wasn't in your favor. If it took too much magic power for one, why not have multiple ppl power it? They even invented a battery for it later so it's failure to take off is dumb.
If they did proper testing they would have known that a waterwheel wouldn't work underwater.
They built full scale models, without proper testing, or proving the concepts crucial to the idea. It is no wonder why they ran out of funds to complete it and couldn't sell it. The craftsmen were incompetent.