This is the Naupaka Kahakai flower, it’s very common around the coastal areas of the Big island and if you look closely you’ll notice it appears to be half a flower. Click on this link to read the legend of the Naupaka flower, a story of two lovers, and why it’s only a half flower.
I found the Naupaka Kahakai flower on the way back to my car while down at Kukio to photograph a watersports/running race. This is looking towards the Kua Bay area from Kukio. Kua Bay is on the other side of that rocky coastal area.