In tropical regions, jellyfish envenomation is a persistent hazard for people who spend time in the sea. Jellyfish stings can be dangerous, and among the people who face the greatest risk are scuba divers. This study therefore sought to determine the level of knowledge divers in Thailand have about the threat of jellyfish envenomation.In April 2018, a total of 238 divers responded to a questionnaire, thereby providing data for further statistical analysis.The findings revealed that 31.91% of the study participants cited jellyfish stings as their most frequently encountered injury, with 68.09% having personal experience of the problem, or having seen others injured by jellyfish. However, 34.03% of the sample respondents believed their own level of knowledge to be "low" or "none". The mean score was 71%, which can be considered satisfactory, but the scores for items concerning the recognition of signs of envenomation and items about first aid responses (52.74% and 59.13%, respectively) were not acceptable.Divers frequently experience jellyfish stings, and diving personnel were highly rated for their knowledge in this area. However, very few were fully confident in their first aid capabilities, and therefore it can be argued that it is necessary to improve the level of medical education and to provide training to eliminate this weakness.