Jellyfish are not nearly as dangerous and menacing as they are perceived to be. Many species are, in fact, harmless to humans and are mostly gelatinous masses that peacefully make their way through all our world's oceans. Jellyfish are NOT fish and are essentially 95% water. While they are very simple creatures (lacking a heart, lungs, or nervous system), they do have nematocysts, or stinging cells. These nematocysts are what cause the uncomfortable burning or itching sensation when we come too close to our floating friends. Although jellyfish do not have a brain, they have somehow survived living on the earth for 500 million years. The following are a few species you may find while surfing, snorkeling, or swimming in the Pacific. Moon Jellyfish: This species can be found abundantly almost anywhere in the Northern Hemisphere. The venom these jellyfish produce is not harmful to humans, and they are considered a delicacy in some parts of Asia. They can reach 30-40 cm. Moon jellies survive well in aquariums, contrary to most species.Box Jellyfish: Along many Hawaiian beaches you may see signs warning of the dangers of Box Jellies. They tend to arrive within 9-12 days after a full moon. They are named because of their squared shape but are relatively small and difficult to spot in the water. For that reason, it is not recommend to swim in remote beaches where help cannot be called in case of a sting. Lagoon Jellyfish: The top of their bell is approximately 5 inches in diameter and they are considered to be much less harmful to humans compared to other species. Originally native to the Western Pacific, they were introduced to Hawaiian coasts through ship ballast waters. Further research needs to be done on this species. Portuguese Man-o-War*: The tentacles, on average, can be 30 feet, but tendrils reaching 165 feet have been recorded. For humans, this sting is rarely deadly but can be excruciatingly painful. Even those specimens that wash up on shore can still deliver a sting. They can travel in groups of over 1,000 and use the nematocysts in their tendrils to paralyze or stun fish.*Portuguese Man-o-War are not considered to be jellyfish and are actually a colony of organisms working symbiotically. What to do if stung by a jellyfish:Remove the tentacles in contact with skin and rinse the area with clean hot water or vinegar (to deactivate the toxins). Call for help to prevent a severe allergic reactions.