Nudibranchs are often casually called "sea slugs". They are very numerous in terms of species and are often very attactive and noticeable. Because of their often very bright colouring they can usually be found quite easily. However, with their size ranging from only 20 to 600 mm. (0.79 to 24 inch) that obviously isn't always the case. The intense and bright coloured ones found in South Australian water, warn other species with their colours that they are very distasteful or poisonous (but they are in no way dangerous for humans).