This is figured in Gosliner et al (1996) as Eunice cf australis. A recent revision of the family caused its members to be split into several genera, and now it requires examination of the jaws and chaetae to properly place them. These are common under rocks on many lagoon, pinnacle and seaward reefs.
The Eunicid is the one crawling under the other worm in the photo.
Created 1 February 2019
Updated 10 September 2021