Typically attached to sharks and rays leaving obvious scars, rarely found on the seafloor presumably awaiting a new host.    Warty with tapering ends, brown, often with rows of orange or pale spots.  My wife was swimming along a shallow coral reef at Kawaihae, Hawaii, when an orange spotted leech charged at her but she was able to swat it away, preventing it from trying to attach.  Attains at least 3 inches.  Warm seas worldwide.