## Pearl Diving (or similar sea-based resources) ##

There is a reef off the north coast that has a unique and valuable shellfish species, and the northerners job is diving for them.

Exactly why these shellfish are so valuable could vary. Pearls are the obvious answer - top-quality natural pearls can sell for thousands or even millions of dollars each ([La Peregrina][2] sold for over $10,000,000 in 2011, but that is with significant historical significance on top of its raw value). On the other hand, a historical story might use [Tyrian Purple][1], while a modern or sci-fi take could give them pharmaceutical properties (imagine how valuable an anti-aging drug or reliable cure for cancer would be) - or if you want to double down on how evil the bad guys are, they're the key ingredient in a new, dangerous, but highly-addictive illegal drug.

Regardless of why they're valuable, this species has very specific habitat requirements that mean they can't be farmed (or, in the case of pearls, farmed ones are considered 'cheap knockoffs'), so they must be harvested in the wild.

Reasons why this is unpleasant and exploitative can be tailored to your story needs, but could include:

 - The workers are paid pennies for recovering a product worth a fortune. (Supposedly the worker who found La Peregrina in the 1500s was rewarded with 'his freedom') This one is obvious, but included for completeness.
 - The sea where the shellfish are harvested is particularly dangerous, due to currents, weather, temperature, or some combination of all three. This likely fits well with your note in the food section about the north having a terrible shoreline - only a mad or desperate person would swim off North IU, but that's the only place where Union Rainbow Pearls are found...
 - Technological assistance isn't possible. There's no way to harvest these with nets or lines from the surface, and they're too fragile or difficult for a robot to handle, so a diver is needed. Perhaps they live in caves or reef crevices that are barely large enough for a human, so SCUBA gear is too bulky - or the gear *can* be used, but there's a major risk of death-by-snagged-air-hose.
 - Alternatively, the assistance *is* possible - perhaps an automated harvester has recently been developed - but the exploited group can't afford it themselves, and the exploiters don't want to pay.
 - The flora and fauna in the area are particularly dangerous. Sharks, sea snakes, salt-water crocodiles, tangled kelp forests, merfolk, krakens... whatever it is, as above, only a madman swims off North IU.
 - The shellfish *themselves* are dangerous - perhaps they have venomous claws/spines or are just highly poisonous to the touch. If they're valuable because of some chemical that can be harvested, the dangerous part may well be the reason they are so valuable in the first place.

  [1]: https://en.wikipedia.org/wiki/Tyrian_purple
  [2]: https://en.wikipedia.org/wiki/La_Peregrina_pearl