It's Pogostemon erectum. It matches a good botanical description and herbarium specimens I've found. I've seen preserved Rotala verticillaris and it's easy to see why they were confused. The inflorescences aren't at all the same though.
Yeah, I keyed it out based on a good botanical description and everything matches. Both that and the Rotala are from the same general area, so it's easy to see how that might have contributed to the confusion.
This is a really lousy (as usual) photo of a REAL Rotala verticillaris botanical specimen using my camera phone. A friend of mine may have a much better one. The flowers are actually there, but they're very tiny and sessile (right up against the stem). Not all like P. erectum. The specimens are emersed.