Anime based on the book TheSwissFamilyRobinson about a family which gets stuck on a tropical island after a shipwreck and have all sorts of adventures there.

While there, they build a huge treehouse. As they explore the island, they find out they're not the only ones stuck there.
!!This anime provides exampes of:
* DesertedIsland
* FloatingInABubble: OP only
* LensFlare: OP
* TwiceToldTale