Poisonous jellyfish are found on the beaches of Alicante, Playa San Juan, Benidorm and Ibiza. These dangerous jellyfish were found washed up on these local beaches and also have been sighted in the waters so the beaches have been temporally closed to the public as a precaution Swimmers and surfers have been advised not to enter the waters until the jellyfish have left the Spanish coastline and made their way back to the Atlantic Ocean. The tentacles of these poisonous jellyfish can grow to an incredible length of 30 meters if left in the right environment. The Portuguese man of war (Physalia physalis) jellyfish usually found in the Atlantic Ocean, which is also known as the man-of-war or by another name of floating terror, is a marine hydrozoan and part of the family of Physaliidae most commonly found in the Atlantic Ocean, Pacific Oceans and the Indian Ocean. These jellyfish are highly venomous and poisonous, the tentacles are very long and have a very painful sting if touched. Leaving marks on the skin and even difficult scars to reduce and in some extremely rare occasions, the powerful sting has been known to be fatal to humans.

The Indo-Pacific Portuguese man-of-war or blue bottle is a related species with a very similar appearance found throughout the Indian and Pacific Oceans. The most characteristic of this false jellyfish is the way it is, it has two parts to the body part (1) a bottle-shaped body, bluely purple translucent in colour that floats above the water line, part (2) while the other remains submerged with the extreme long tentacles under water. It's not uncommon to see jellyfish at this time of the year but as it is still out of the official swimming season, everyone is confident that they will all shortly disperse from the Spanish Costas.