We jumped off the boat and swam through a narrow arch in the outcrop known as No Man’s Land, then struck out for Old Harry, the towering sea stack that gives the iconic chalk formation its name. Though primarily known as a site of geological interest, Old Harry Rocks is also significant for its biodiversity both above and below the waves. The water was crystal clear, and as I glided above the luxuriant seagrass meadow, I scanned the vegetation, hoping to glimpse a seahorse.
This stretch of coast is a stronghold for short‐snouted and long-snouted (spiny) seahorses, and the largest specimen recorded worldwide – a 34cm-long spiny – was found here in 2015. Alas, the elusive creatures remained hidden among the eelgrass, but there were plenty of brown crabs scuttling about and a fist-sized, spindly-limbed spiny spider crab picking a path through ribbons of kelp. As the current swooshed me through another archway, I rolled on to my back and gazed up at the looming cliffs.
Spotting the distinctive spitfire-like silhouette of a house martin against the sheer rock face, I watched it swoop up, its white rump disappearing under a 30ft-high ledge. In Macbeth, Banquo speaks of “the temple-haunting martlet”, and this charismatic little hirundine’s common name reflects the species’s long association with human dwellings. But while they now nest almost exclusively in the eaves of buildings, a few colonies can still be found nesting wild, like their ancestors, on coastal cliffs.