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").
Rhopilema nomadica
Rhopilema nomadica, the nomad jellyfish, is a jellyfish indigenous to tropical warm waters of the Indian and Pacific Oceans. Since 1970's it has been also found in Mediterranean Sea, where it entered via the Suez Canal. It has been found in the Eastern Mediterranean, off the coast of Israel, Turkey and in the Aegean Sea off the coast of Greece. "R. nomadica"'s body is light blue and the bell is rounded. It can grow up to 10 kg of weight, and its bell is commonly 40–60 cm in diameter, but can be up to 90 cm. European Union lists it as one of the worst invasive marine species in European waters.