Dobfin

During the Roman conquest of Ancient Dakias, the Romans had to inflict a blockade on the Dakian maritime trade market, primarily from the coast of Dobruja. In order to enforce it, they loaded the waters with Dobfin. They were domesticated to recognise a certain scent only the Romans had, and without it they attacked any ship passing through.

In the modern day, they swim around the Dobrujan coast and search for trinkets stuck into the sand. They dig them out and let them resurface for the land dwellers to claim.