So funny ! It s not jelly , not fish . But its name is Jellyfish . They are found in every sea , ocean , freshwater lakes and rivers . They grow on rocks . Two principal activities : swimming and eating . Their tentacles bring food towards the single orifice . Most jellyfish stings don t hurt humans , but some may cause agony . Irukandji Jellyfish got 100 times poison than a cobra . Be careful when you go swimming .