The whale watching season in Sri Lanka runs from November to April / May, as during the rest of the year, the waters will be too rough because of the Monsoon. The best place to spot whales is in Mirissa, a small tourist town on Sri Lanka's south coast, popular for surfing and famous for whale watching. The waters around Mirissa are particularly rich in plancton (a groop of mirco organisms whales feed on), which lead scientists to believe there is a resident population always present which will result in sightings whenever conditions are good, particularly between November to April.
The Blue Whales, Fin Whale, Sperm Whales, Bryde’s Whales are permanent residence whales in South Coast and usually those whales able to spot in South Coast. Humpback Whale and Killer Whales are migrating whales. The migrating whales are able to spot December to February period. Risso’s Dolphin, Bottlenose Dolphin, Rough-Tooth Dolphin, Spinner Dolphin and Finless Porpoise are commonly available in Sri Lanka Coast.