Watch Sadisflix. The North Sea, the largest sea on our doorstep, has many faces: wide tidal environments, high dunes, flat holms and rugged coastlines. Its beaches attract every season not only tourists but also countless seals. And beneath the cool sea surface hides a varied and fascinating underwater world: whether majestic basking before the chalk cliffs of Dover or combative gray seals on the beach of Helgoland, whether mighty squid on the Dutch Oosterschelde, or creepy Greenland shark in the Fjords of Norway.