Sea shell contain calcium carbonate. He can use that's to make a slaked lime. First,he must scrape the sea shell to produce a powder from sea shell that contain calcium carbonate. Second,he must heat the powder of calcium carbonate that will turn to calcium oxide solid. After that,he must put the powder which is heated by lighter or else in water.If water is added to the calcium oxide solid,calcium hydroxide solution(slaked lime) is produced.
--sorry if got language mistakes--