"Swimmer's itch is a patchy red pinpoint skin rash associated with itching on the parts of the body that have been in the water. Swimmer's itch is usually not severe. After the initial transient itching it will disappear without treatment. The itching occurs within 48 hours and may last up to 7 days. Rarely, it can be severe if a large proportion of the body is affected. The major, although not the only, cause of swimmer's itch are trematode parasites of aquatic/migrating birds. The life cycles of these parasites involve snails as the first host and aquatic birds or some mammals as the final host."
- From a medical website.
Yes folks, I have had "Swimmer's itch".
I contracted it while swimming in a lake Wisconsin - in 1983.
I was swimming around (not across) the lake with a high school buddy, with two young ladies in a rowboat spotting us. We swam a mile and a quarter to a lakeside convenience store, bought supplies and then we rowed back. One of the young ladies, who I did no know, said she enjoyed watching my muscles as I swam. Adroit young man that I was (read: no clue), I took this at face value and did not pursue.
But I did contract swimmer's itch.