I found the meaning of it...
Geronimo was the English name given to a Native American who famously took revenge on Mexicans who killed his family. Sheppard uses the term in this song for a different reason. Soldiers who jump out of planes often shout “Geronimo!” as a way of communicating that they are fearless. This term invokes that connotation in this song: taking a leap fearlessly into the unknown.“Bombs away” is another expression that carries the same connotations of “Geronimo.”

Sheppard indicates that the fearless leap into the unknown in this song refers to love, which is always a rush, but never without its risks.

The pursuit of love in the relationship moved too fast, causing problems.

The waterfall only provides imagery; it is not a metaphor for something.