Researchers on the Big Island have drilled and found an enormous unexpected supply of fresh water. Why does this matter for Maui real estate? Because water limitations are frequently cited as a reason for stopping development and because the same researches believe Maui may have a similar geologic formation:

Thomas says now that scientists realize how little they know about the islands, they cannot say confidently that similar fresh layers exist elsewhere. But he thinks there’s a good chance on Maui, where Haleakala lava overlies West Maui lava.
The alluvial Central Valley does not easily reveal where the best place might be to drill, but Thomas would like to do an assessment to determine a couple of likely sites.

Hmmm