There is a long European history of collecting and enjoying shellfish, in fact far more so in the past than today. Oysters, for example, were an everyday food until the early 20th century, widely enjoyed by people in all walks of society until supply problems and growing pollution saw them fall rapidly out of favour.
Today though, a huge variety of great quality molluscan shellfish is readily available, be they bivalves such as Mussel, Oyster and Scallop or Gastropods (members of the snail family) with one shell, such as Limpets and Whelk. Whether farmed or harvested from the wild, shellfish are a worthy addition to any menu and almost universally popular once again.
As filter feeders or bottom grazers, Gastropods can bioaccumulate toxins which is why many Molluscs eaten in the UK are first purified to ensure they are safer to eat.