Box jellyfish
In Australia (mainly northern; however, box jellyfish can live in subtropical waters as far south as Sydney, with "Carybdea marsupialis" being recorded as far south as Bermagui, Sapphire Coast) the highest risk period for the box jellyfish is between October and May, but stings and specimens have been reported all months of the year. Similarly, the highest risk conditions are those with calm water and a light, onshore breeze; however, stings and specimens have been reported in all conditions.
Ada Ciganlija
These anthomedusae begin their life as polyps and develop into jellyfish only if conditions, such as purity and water temperature over 25 °C, are right. However, authorities claim that these harmless and almost invisible jellyfish (they are only to wide, bell is in diameter and have no sting cells) actually have been present in the lake for over 20 years. The first specimens were discovered in 1994 and they can also be found in the Danube. They live only for several days.