Know before you go...
Swimming in the pool below the waterfall is highly discouraged and prohibited because there is a threat of becoming infected with Leptospirosis due to the water being stagnant and a collection of all sorts of bacteria.
The area is also prone to rock slides.
There is no entrance fee, but there is a $5 parking fee if you use the lot by the Manoa Falls trailhead.
The entire easy hike will take about 1-2 hours roundtrip, depending on how muddy the trail is, how fit you are, and how long you linger at the waterfall.
The best time to visit is always during the summer months in the morning.
As you hike, you will feel the early morning mist, fresh air, and sunshine overhead through the lush greenery. In the afternoon, it can be a little bit chilly if you want to take a dip.