We named him Squirt – not because he was the smallest of the 16 cuttlefish in the pool, but because anyone with the audacity to scoop him into a separate tank to study him was likely to get soaked.

In the new Prime documentary series “Octopus!” actress Phoebe Waller-Bridge spends an hour and a half narrating a story about an octopus named Doris that sets out on her own, falls in love and ...