Complex sentence: Until recently, the natural entrance was not owned by Howe caverns but now that the entire cave is owned, plans are being set to continue the boat ride and have the tour exit out of the natural cave entrance.
Split into simpler sentences: Until recently, the natural entrance was not owned by Howe caverns but now that the entire cave is owned. Plans are being set to continue the boat ride and have the tour exit out of the natural cave entrance.