Indeed , box jelly fish are the big danger in South East Asia . 60-70 people die each year in the Philippines . Also 5 deaths is Thailand since the 1990s, mostly around Koh Samui area . Box jelly fish are difficult to see as they are translucent . Often in shallow waters . Can kill in seconds or up to 48 hours after a sting . Vinegar application asap and sting removal with tweezers can help . Many Thai beaches have vinegar stations . Some beach hotels have nets in the sea to prevent jelly fish entry . One of the reasons that Thai people are often seen swimming fully clothed , is to prevent stings .
Most European tourists are unaware of the dangers in swimming in Thailand's seas , both in the Andaman sea and the Gulf of Thailand . Not only sea creatures but also rip tides etc .