The boat is swinging like a skidding car as it makes it way down a channel lined by dark grey cliffs. I can hear the engine is gunning but progress is painfully slow. This is where currents meet, two powerful columns of water crashing and somersaulting together in a washing machine of briny muscle.

The surface of the water is taut, occasionally breaking into an angry swirl or rising into sharp spikes like the hundred black dorsal fins of fish stranded by the tide. The engine revs again and we are free, surging towards the turquoise stillness of the lagoon with its bright, white-shell sand and rocks holding waving seals.

Intrigued they slip their sausage bodies into the water, their heads bobbing to the surface closer to the boat, whiskers webbed with water and dark eyes you could almost drown in. They are mermaids with the faces of labradors.

Later we hit the swell of the sea proper. Greasy lumps of water shrug the boat into wallowing troughs, the spray hissing and leaping over 90ft cliffs.  We manoeuvre into a sea cave, the walls petrol-washed with star bursts of metallic ore that burst through a powdered mist of cormorant shit.

We shout to try and hear the echoes but the sea, always louder, shouts back.