Poseidon's Amulet

If there is a map with a cross and a legend about pirates, then there must be treasure! For Lena, Fritz, and Mari, this idea somewhat brightens up a very boring excursion to the island, where they hear the legend and find the map. However, as they begin their search for the treasure, they discover that an incredible treasure is actually hidden near the island - an amulet of incredible power that grants control over the seas. But it is already being sought by a sinister sea witch! Who will be the first to reach the amulet?