Special make-up supervisor John Vulich considered the monster with its translucent tentacles as the hardest thing he had to do all season.
Gillian Anderson later joked that they got so wet in this episode, it was like being back in Vancouver.
Six pairs of costumes were required for each cast member to replace all the wet clothing.
"Agua Mala" is Spanish for bad water and in some Latin American countries is slang for "Portuguese Man-of-War", otherwise known as a blue bottle (Physalia Physalis), a marine hydrozan.
Eight water towers with sprinkler bars were used on set to create the appropriately wet weather conditions. These, along with the numerous wind machines, meant that the sets were completely destroyed by the time filming had finished.
