archman:Unlike other jellies, cubozoans have EYES, and use them to move towards potential food (i.e. people). Yuk!
Actually they have 8 eyes. Four looking into their "stomach" and four looking outwards. Weird!

Growing up in the most poisonous corner of the Earth I'm not really too bothered by most of this stuff. Understand your environment and take the appropriate precautions and you'll be fine (I managed to survive a pretty wild childhood!

The box jellyfish are more dangerous to your average swimmer due to the shear number of "stings" it can administer with it's extremely long tentacles. A great way to die is to wade into the ocean on a calm summers day, get stung on the legs, reach down to rub the origin of the pain, get stung on your arms and hands and then drag the tentacles up onto your chest! :11: A friend of mine suffered more than a meters worth of sting and went to the hospital for months. He still has the scars on his arms and legs today!
The Irukandji is more likely to affect divers as it inhabits waters further from shore. It's related to the box jelly. The effects of its venom are different, in particular the delayed reaction. The pain is supposed to be as severe as you can get once it gets going! It's really small (only about 2 cm total size) but still packs a wallop! There's only been a few recorded fatalities but from what I understand, most people wish they were dead while enduring the pain (which cannot be treated either effectively or safely with morphine or other powerful painkillers) . If you're really concerned then wear a skin, booties and gloves and hope you don't put your face into one!
As others have mentioned, the box jelly "family" is all over so it doesn't surprise me they'd be in Thailand too.
BTW, I noticed a few people talking about Scorpion fish as though they are going to get up and come after you. :06: I thought the danger was standing or putting your hand on them?