Beautiful Jellyfish

1. 

Portuguese man o' war can be found in the Atlantic, Indian and Pacific Oceans. It can kill fish or, rarely, humans with its venom. Despite its appearance, it's not a true jellyfish, because it's not a single multicellular organism. Man o' War floats on the surface of the water, leaving its tendrils to sweep the depths below for plankton and fish.  It is translucent, and is tinged blue, purple, pink, or mauve; may be 3.5 to 11.8 inches ((9 to 30 cm)) long and may extend as much as 5.9 inches ((15cm)) above the water. Tentacles are typically 33 ft ((10m)) in length, but can reach over 98 ft ((30m)).

2. 

Crown jellyfish is one of the most venomous jellyfish species even they are 95-99% water based. They are mostly blue and purple coloured and like cold water. They usually stay down where it's cold in the Pacific and Atlantic Oceans. 

They are able to make light through bioluminescence. Their bells light up, when they are touched. Otherwise, the bell with maximum size 19-23 inches ((50-60cm)) will look transparent.

3. 

Lion's mane jellyfish is the largest known species of jellyfish. Its range is confident to cold, boreal waters od Arctic, northern Atlantic and northern Pacific Oceans. The largest recorded specimen had a bell with a diameter od 7ft 6in ((2,3m)) and tentacles 120 ft ((37m)) long.Large individuals are often red or purple, while smaller specimens tend to be shades of tannish-orange.

4. 

Halitrephes maasi was found 4,019 ft  ((1225m)) below sea level. It reflects light with bright splashes of yellow and pink. Without light it drifts unseen in the dark.