Well, we came up with the idea that maybe a visible passage way could be seen through the Waterfall. We then jump into the water and swim to it! Once on through the waterfall, we will be in a new room.
In addition to this, there will be about 6-10 new rooms on that side of the island! The map for the other island would be replaced with the map for that side of the island! (or you could flip it).

I'd really like to hear what you guys think about this! I think it's a pretty good idea, but that's my opinion.