Common tortoise limpet
Some snail species are not particularly snail like. The limpets are different from other slugs in that the shell is cap-shaped but not coiled. Their underside is like a suction cup and they use that to attach themselves to rocks and seaweed. They can tolerate quite high wave activity due to this. This is also their defence against predators because they are extremely difficult to unleash.
The common tortoise limped is the most common species in Icelandic waters. It is common on rocky shorelines and in kelp forests in shallow seas all around Iceland. There, they feed by scraping up algae. The common tortoise limped is found throughout the northern hemisphere, both in the Atlantic and the Pacific.