Opihi Bay lies at the head of the north-west arm of Port Underwood.
It has a nice long beach backed by pine tree plantations and is a fantastic beach to swim at during summer.
The shoreline is surrounded mainly by native vegetation, the most notable of which is the New Zealand Flax, or Harakeke in Māori.
White-faced heron, gulls and South Island oystercatchers can often be seen feeding along the shoreline or in the shallows.
Anchorage in Opihi Bay can be pleasant and the holding is good. However, this bay can be a wind tunnel and it can therefore be uncomfortable anchoring here in strong winds.
Good anchorage in a southerly is on the eastern side of the bay and is also pleasant in a NW.
Accessible primarily by boat, there is private land between the road and the beach.