The students were all aboard a large ferry which was sailing through an area dotted with small, uninhabited islands when a freak storm struck and they had to abandon ship. They drifted for days and finally washed up on the shore of a previously unknown island. They staggered out of their lifeboat and found, to their great surprise, that the island was inhabited. The locals had reached a high level of sophistication, and had a thriving economy, but they had not developed any desire to leave the island or explore and so they had remained cut off from the world as we know it.
The castaways thought that there was no way for them to leave until they were befriended by a local fisherman. He offered to help them by renting them a small boat and a house each. He told them they could use the boats to make money by becoming lobster fishermen - the island's major industry. The fisherman explained the basics of lobster fishing to them and showed them where the two main fishing areas are. He told them that they could sell the lobsters they catch to the other islanders and then buy one of the light aircraft used by the locals with the profit - flying is the national pastime here!
This is the situation that the players find themselves in at the beginning of the game. Each player has £100 with which they can buy some lobster pots. They can then use these pots to catch lobsters to make money. At the end of the week they must pay all their bills for things like rent and fuel and any money they have left over they can re-invest into more lobster pots or put on one side in case they need it later.