Every summer, a massive jellyfish known as Rhopilema nomadica, which can grow as large as a hat and weigh up to 10 kilograms, returns to the coasts of the Eastern Mediterranean. These jellyfish travel in vast shoals that can stretch for tens of kilometers, and in some cases, up to 100 kilometers. Their stinging tentacles can cause painful burns to swimmers, sometimes leaving marks that last several days. This species is not native to the Mediterranean; it comes from the Red Sea, crossing over through the Suez Canal, a process known as the Lessepsian migration, named after the French engineer who built the canal in 1869. The Suez Canal initially had natural barriers—salt lakes—that prevented most marine life from crossing. However, over time, the salt concentration in those lakes decreased, weakening this barrier. In recent decades, the canal has been widened to allow larger ships to pass, increasing the flow of water and facilitating the migration of species from the Red Sea into the Mediterranean. The nomadic jellyfish first appeared in the Eastern Mediterranean in the 1970s, off the coast of Israel, and has since become a significant summer phenomenon, affecting areas from Lebanon, Syria, Egypt, and Turkey. It moves westward each year, carried by coastal currents that flow from south to north. The jellyfish's presence has created challenges for both people and industries. Local fishermen report that their nets quickly fill with the creatures, making their catch unsellable. Power plants that use seawater for cooling also face repeated issues with clogged filters, especially along Israel's and Lebanon's coasts. The jellyfish thrives in warm, salty, and oxygen-poor water—conditions that are becoming more common in the Eastern Mediterranean due to climate change and rising sea temperatures. The migration of the nomadic jellyfish is part of a larger trend: hundreds of species from the Red Sea have moved into the Mediterranean through the Suez Canal. These invasive species are changing the region's ecosystems. For example, the lionfish, with its striped appearance and venomous spines, has established itself in the rocky areas of the Eastern Mediterranean, where it has few natural predators. The rabbitfish, which eats large amounts of seagrass, has contributed to the loss of underwater vegetation in some areas, replacing it with exposed rocky seabeds. Scientists have noted that the number of Red Sea species in the Mediterranean continues to rise each year. While the Western Mediterranean remains relatively unaffected due to its cooler temperatures, the Eastern basin is increasingly dominated by these newcomers. Despite the ecological changes, closing or re-salinating the Suez Canal has not been considered seriously, as it is one of the world’s most important shipping routes. Instead, Egypt has continued to widen and deepen the canal, maintaining the flow of water between the two seas. For over 150 years, the current has flowed in one direction, bringing species from the Red Sea into the Mediterranean.