I've never been to Maunawili falls, but if I go, I don't think I'll jump in. The first case of leptospirosis I saw after practicing here for about a year was an older man in the ICU with liver and kidney failure. This is one extreme of the disease, but if you are exposed, it's not clear who will get simple flu-like symptoms and who will get much sicker. So, be safe, and keep your mucous membranes and skin abrasions ouit of the mud and water, especially if you're going to Maunawili falls. Maybe it would be a good idea to keep a list of swimming holes known to have Leptospirosis and post the list on Dayles hiking page.
Common sense counts for a lot.
Knowing about a questionable exposure area in advance or just to be on the safe side, a little doxycycline in advance and afterwards is good for your piece of mind to be on the safe side. They missed the Olympus trail and ended up coming down Palolo. The water was long gone.