Attaches to sharks, rays, turtles and, given the chance, divers.
To about 110 cm, slender and dark grey-brown with a white-edged black stripe running the length of the body, and a ridged oval sucking disc on top of the head — a modified first dorsal fin — used to hold onto a host. Free-swimming individuals are common and the disc is visible from above.
It attaches to sharks, rays, turtles, large groupers and boat hulls, feeding on the host’s parasites, scraps and faeces, and detaches to forage independently. It will attempt to attach to a diver, usually to a tank or a wetsuit, and can be persistent; there is no harm in it, but it is difficult to shake. Juveniles are often found riding a single host for long periods. Recorded from the shallows to about 45 m.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.