box jellyfish

Yesterday on bottle beach,Koh phangnan,thailand.I saw small jelly,about 4 or 5 inches in diameter,washed up on the sand.it was translucent with slightly pinkish gonads(?).I did not see any tenticals.the water seemed much warmer and more brackish than the day before,and there had been rain at least two nights in a row.two children were stung;a girl and a boy.I do not know what happened to the girl,the little French boy died.