Sri Lanka is possibly the best place to see blue whales and sperm whales in the world (see here for a good trip report and related issues). Increased sightings of both blue whales and sperm whales off the southern coast of the island have now opened up a window of opportunity for whale watching tourism in the island’s Deep South. More here
A high concentration of blue whales and sperm whales have been spotted in the seas off Dondra Head along the deep south coast of Sri Lanka, during the months of January to April. Some of the blue whales off Dondra Head could be resident whales while others could be migratory ones crossing over to the Arabian Sea from the Bay of Bengal.
This company offers 8-day trips with a naturalist (exl. flight) for £690.