According to Zenock, Neum, and Zenos, when Jesus is crucified there will be a sign to the people who live on islands. What will that sign be?

Three days of darkness

According to the words of Zenock, ... Neum, and ... Zenos, ... three days of darkness, which should be a sign given of his death unto those who should inhabit the isles of the sea. 1 Nephi 19:10