This films starts with an animated sequence that happens in the 17th century and shows how a boy was captures by a slave boat and taken to a Caribbean island, where he hides a map in a jar, before being taken to work in the sugar cane fields. Now in life action and present day, a family of four in getting ready to leave the house in order to have a picnic near a lagoon. The two friends arrive and they all drive to the Condado Lagoon in San Juan. The children start playing and one of them finds a jar with a map inside. So without their parent's permission, the four children decide to embark on an adventure through the Estuary of San Juan, thinking they will find a treasure if they follow the map. They cross a lagoon on a raft, then they find a sailboat and ask the captain to take them to the other side of the San Juan Bay. From there they walk to a marshland and cross it even though their legs are half way in the mud.