In my high fantasy medieval world, the ocean is populated by underwater fish people and land dominated by your good old human. Different type of fish people (shark, whale, turtle, shellfish, etc.) live at different depths, and forming their own kingdoms. Several kings would sometimes band together, forming a massive alliance that spanned across the ocean.
What I'm curious about is how would trading look like, both the trade with other underwater kingdoms, and trading with humans. How would the age of sail different now that there are multiple powerful kingdoms under the ocean? Note that neither human nor fish people are capable of fully engage each other, as there is currently no means for human to push their forces deep enough underwater, and the fish people are unable to leave water for too long. Piracy, however, is very much possible, and I envision fish people are going to be doing most of the raiding. The trade routes between underwater kingdoms are too deep undersea for human to raid.
The fish people could leave the water, but only for a short period of time through the use of magic. So I imagine there'd be trading ports that are partly submerged, sort of kind of like Venice, and trading between human and fish people can be conducted there.
Now I know there are a lot of stuff people want from under the ocean, pearls and what not. But what would the fish people need from people up above? What kind of quality goods would they be looking for?
And how would trade looks like between human kingdoms oversea? Would they stay pretty much the same, with the only difference that now there are fish pirates?
I imagine the underwater currents might serve as the trade routes between underwater kingdoms, as a mean of quickly getting goods from one place to another. They'd probably be using muscle beasts, sort of like the counterpart of human trade caravan. How would their ships look like?
To sum up my question:
- How would trade look like (methods, trade-route locations, ships, etc.) between:
- humans and other humans oversea
- humans and fish people
- fish people and other fish people undersea
- What would the fish people seek to gain from trading with humans?
- Other interactions you can think of that related somewhat to trade? Piracy, mercenary, slave-trade, fish people eating humans and humans eating them back as a delicacy, etc.