How they COULD HAVE got there Story:
After Fishing came and the new island said to be Raven's Cove, an East India Trading Co. Treasure Fleet launched. The Conqueror was on the verge of sinking, so a Tyrant did an emergency offload of treasure by dumping it with the Legendary Dagger in it without the key to the chest. It was set adrift and went into the suction of Isla de la Avaricia and rested on top of a rock below the surface. Many ships from the French, the Spanish, and Pirates tried to hook it but they miss and nearly run aground. Pirates on land can't get to it since the waters around it is chillier than the rest of the Caribbean Waters. To this day, the Chest and pouch lay wet and cold since the Legendary Dagger is inside it.
Unknown if True Story.