Two young adults presented an interdigital intertrigo and a dyschromic nail alteration, respectively. They were adept of intense sport swimming in pools. Lesions had been misdiagnosed as athlete's foot and onychomycosis, respectively. Several antifungal treatments had been tried without success. After many months of inadequate management, the dermatological examination revealed the presence of two malignant melanomas corresponding to the eroded acrolentiginous and nodular subungueal types, respectively.