The Hamlet (Hypoplectrus), is a grouping fish that is found mainly in coral reefs in the Caribbean Sea and the Gulf of Mexico, particularly around Florida and the Bahamas.
Hamlets are simultaneous hermaphrodites (or synchronous hermaphrodites): They have both male and female sexual organs at the same time as an adult. They seem quite at ease mating in front of divers, allowing observations in the wild to occur readily. They do not practice self-fertilization, but when they find a mate, the pair takes turns between which one acts as the male and which acts as the female through multiple matings, usually over the course of several nights.
It’s a popular choice for hobbyist saltwater aquariums.