### In some ways, this spell is more powerful than the *wish* spell. 

The spell *wish* is the most powerful, indeed, its description states:

>Wish is the mightiest spell a mortal creature can cast. By simply speaking aloud, you can alter the very foundations of reality in accord with your desires.

One of the stated functions of *wish* is:

>You create one object of up to 25,000 gp in value that isn't a magic item. The object can be no more than 300 feet in any dimension, and it appears in an unoccupied space you can see on the ground.

So in a world without your *spectral vessel* spell, the only arcane technique that can conjure a ship is "the mightiest spell a mortal creature can cast". However, when it comes raising destroyed naval vessels, your spell *is much better* even than *wish*. 

*Wish* has a 25,000 gp limit (unless opting to use an "off-label" use of *wish*, see my answer [here](https://rpg.stackexchange.com/a/185204/62294) for details), but the value of a high quality ship can *far exceed* that limit: 

>Adding an upgrade costs 15,000 gp and requires 1d4 weeks of work.
>
>-*Ghosts of Saltmarsh*, "Superior Ship Upgrades"

And your spell can be cast without the consequences of using *wish*:

>The stress of casting this spell to produce any effect other than duplicating another spell weakens you. After enduring that stress, each time you cast a spell until you finish a long rest, you take 1d10 necrotic damage per level of that spell. This damage can't be reduced or prevented in any way. In addition, your Strength drops to 3, if it isn't 3 or lower already, for 2d4 days. For each of those days that you spend resting and doing nothing more than light activity, your remaining recovery time decreases by 2 days. Finally, there is a 33 percent chance that you are unable to cast wish ever again if you suffer this stress.

So is it balanced as a 4th level spell? *It's not even balanced as a 9th level spell*.