Some fish regularly clean others, and wrasse and shrimp appear to specialise in this regard, as do remora, which permanently hang on to their hosts.
en.wikipedia.org Fishing, and especially spearfishing, is banned, hence the creole wrasse, parrotfish and snapper that were gawping at me in the indigo silence.
www.telegraph.co.uk Some wrasse species are aggressive towards small fish and invertebrates, others are reef safe.
en.wikipedia.org If needed, a moon wrasse may dig out a space under a rock by repeatedly swimming through it until it fits without struggle.
en.wikipedia.org They are protogynous hermaphrodites, all starting off as females and changing to males, a process which, for the moon wrasse, takes only 10 days.
en.wikipedia.org