In the summer people like to cool down by swimming. However, swimming may lead to annoying skin reactions, the so called swimmer's dermatoses. We present three different cases: an 8-year-old girl with skin complaints after blue-green algae, a 7-year-old boy with a late immune response after a jellyfish sting and a 40-year-old woman with contact urticaria due to latex in the bathing suit. Swimmer's dermatoses can be experienced as very irritating, but are generally harmless and in most cases recover spontaneously. Recognition is important for reassurance and correct treatment advice. Providing good information about safe swimming/bathing locations is essential for prevention.