Swimmer's Itch is caused by a family of Schistosome parasites with a complex life cycle that has two host stages: An intermediate host snail and a final host bird. Each species of parasite capable of causing swimmer's itch has its own characteristic hosts. Swimmer's itch occurs when the free-swimming “cercaria” (minuscule worms) are emitted by the 1,000's daily from each snail host. Thence they migrate up to the surface looking to infect another avian host to perpetuate their lifecycle. Thus suspended in wait they are likely to attach to and attempt penetrate a passing human body rather than a duck. In which case they die and and cause the nasty set of itchy bumps that can ruin a vacation. Studies have shown the infected snail's parasite emissions begin daily around dawn, are very fragile and survive only for 18-24 hours. Their dispersals decrease over the morning hours and become minimal if at all by noon. This cycle repeats daily.