Three new species of Mysidae are described, taken by hand-net, using SCUBA, from reef habitats in 20-40 m water depth on the KwaZulu-Natal shelf. Idiomysis robustus is the fifth described member of this curious genus, and shares the peculiar body shape of all the other known Idiomysis species. The species is found in small shoals, over low-profile, scattered reef. Kainommatomysis zuluensis is the third described species in this genus. Observations suggest this species does not swarm conspicuously, and it has only been collected by sweeping a handnet among gorgonians and seaweeds. Australerythrops africanus is only the second described species of this genus. It has not been seen over open reef, but is commonly found in small to medium-sized caves, or hovering around the entrance to a cave, in swarms containing hundreds, and sometimes thousands of individuals.