From the spawn island, follow the direction of arrow. You can swim or fly to that direction.
After few seconds you will see the island (the main section of this seed). It look so nice with a lots of tree is first things you will see.
Moreover this island will bring you another surprise, go to the marked point in the picture below (you can find it in the other side of the island). At the sand blocks has been lead by the white arrow and start digging down until you see some water, that is first sign of the begin of mineshaft but before go to mineshaft you must cross a mob spawner (Spider spawner).
In the mineshaft you can find lots of rare ores,good items from chest… To more details please watch video below.