Box jellyfish
Although the notoriously dangerous species of box jellyfish are largely restricted to the tropical Indo-Pacific region, various species of box jellyfish can be found widely in tropical and subtropical oceans, including the Atlantic Ocean and the east Pacific Ocean, with species as far north as California ("Carybdea confusa"), the Mediterranean Sea ("Carybdea marsupialis") and Japan (such as "Chironex yamaguchii"), and as far south as South Africa (for example, "Carybdea branchi") and New Zealand (such as "Copula sivickisi").
Carybdea
Carybdea is the only genus of venomous box jellyfish in the family Carybdeidae. "Carybdea sivickisi" is known as the smallest species in the genus and is sexually dimorphic.As of August 2013, the following genera previously classified in this family have been reassigned to the family Carukiidae: