I am writing some menu labels for a website and I'm not sure if I should use the word "Ship" or "Ships" to identify what is inside the linked databases. Those databases obviously contain more ships, not just a single one. So is it correct to use "Ships Databases" which sounds like "The databases contain ships" or "Ship Databases" which sounds "The databases contain general information about 'ship' items"?
Yes, there is a difference, in that "Ship Databases" is correct ("Ship" is used as a noun modifier) whereas "Ships Databases" is incorrect.
This is because the modifier is always expressed as a singular form.
If you really want to emphasise that the databases are databases of many ships, then you need to use genitive plural, i.e: "Ships' Databases". Inelegant, but not wrong.
You can also use genitive singular, i.e: "Ship's Databases", but that has a different meaning, it refers to many databases related to one ship.