The deep waters off Sri Lanka’s southern coast are among the most biologically productive in the Indian Ocean, lying directly along the migratory route of the blue whale, the largest animal ever to have lived on Earth. Between November and April, Mirissa offers the opportunity to encounter these 30-metre giants feeding in the open ocean, often accompanied by sperm whales, Bryde’s whales, and the occasional sei whale. Even more reliably present are vast superpods of spinner dolphins, thousands of animals leaping and spinning in exuberant aerial displays alongside the bow of your vessel. The morning begins in the pre-dawn darkness as you board a purpose-built whale-watching catamaran and head south into the deep blue, guided by an expert marine naturalist who reads the sea for signs of surface activity, distant blow columns, and the electric chatter of dolphins on the sonar.