You spawn on a small group of three island. In there have some tree and you can craft a small boat to swimming to the larger mushroom island by turn around from the spawn. The mushroom island not exaclly is an large island if you explore it you will see this island have few blocks connected with the mainland. But that is not problem, this mushroom island look so beautiful with an area looking like a bay area and lots of shifting terrain.
Seeds : 1412200450 Work in PE ver0.10.5 or ver0.11.0+