A: Yes, you can swim in the Waikuku River, formerly known as Iao Stream, within the Iao Valley. You'll be surrounded by breathtaking scenery while taking a refreshing dip in the clear, fresh mountain water. The river is particularly popular from late spring to early fall. Just be aware that this area is the wettest spot in Hawaii and prone to flash floods. Weather can change quickly so be sure to pay attention to local weather reports before venturing out.