‘Every square inch is covered in life’: the ageing oil rigs that became marine oases

Built decades ago, California's offshore oil platforms are home to a huge diversity of marine life. Now a debate rages over their future

On a recent August afternoon, Ann Scarborough Bull motored out two miles from the coast of Santa Barbara aboard a research vessel called the Danny C. The marine biologist and her colleagues had an unusual destination in their sights: a disused oil platform that loomed ahead like a forgotten skyscraper reaching up from the horizon.

The team wasn't interested in the platform itself, but what lurked beneath. When they reached the ageing structure, named Holly, they lowered a car-sized remote- controlled vehicle under the waves.