Since the late 18th century, kraken have been depicted in a number of ways, primarily as large octopus-like creatures, and it has often been alleged that Pontoppidan's kraken might have been based on sailors' observations of the giant squid. The Kraken is also depicted to have spikes on its suckers. In the earliest descriptions, however, the creatures were more crab-like[17] than octopus-like, and generally possessed traits that are associated with large whales rather than with giant squid. Some traits of kraken resemble undersea volcanic activity occurring in the Iceland region, including bubbles of water; sudden, dangerous currents; and appearance of new islets