Many snail species that live in the transition zone between the sea and the land blur the boundary between aquatic and terrestrial species. They usually spend most of their lives outside of the sea. Yet, they cannot move far from it, because in one way or other, their livelihoods are tied to the sea.
One such snail is Osilinus turbinatus (Vetigastropoda: Trochidae). This species is very common on rocky coasts of the Mediterranean Sea. Here is one individual at its usual habitat that I filmed in Turkey back in June (yes, the snail is that thing near the center of the screen).
Osilinus turbinatus has traditionally been considered a marine snail. But it seems more comfortable outside the sea than in it as long as it is within reach of occasional waves.
I will write more about Osilinus turbinatus in the future.