Popoia or "Flat Island" is made of a dry coral-bed that has surfaced and developed enough earth to support plant life.
Naupaka Kahakai (now-pa-ka ka-ha-kai) grows in a small bunch on the Northern side of the island and the juice from the leaves works suprisingly well as an anti-fog in your snorkel mask. There is a small cove with a sandy beach for landing your kayak and a trail leads you carefully through the nesting seabirds and past several tide pools. The southern side of the island has a popular surf break for long boarders and a view of the Mokulua Islands.