Tucked into the far eastern end of Weligama Bay, the picture-perfect swathe of sand at the village of Mirissa was formerly the island's most famously "undiscovered" beach. The days when you could expect to have the place almost to yourself are long gone, but although the village now attracts a steady stream of visitors, its beach remains one of the prettiest in the island, with a narrow strip of sand backed by dense palm trees which manage to camouflage all signs of human presence. Mirissa has slowly become an exclusive tourist hot-spot and moves made recently by the local hoteliers to only welcome tourists to their hotels has been met in a hostile way and in turn haltered. Most of these small hotels and guest houses are concentrated in a much smaller area than Weligama which makes Mirissa a bit more livelier, hence the popularity. There's reasonable swimming, though conditions vary considerably along different parts of the beach, so it's recommended you get advice about where's safe to swim before venturing into the water. You can also snorkel here, though you won't see much apart from the occasional pretty fish.
Whale watching in Sri Lanka has received a boost with the identification of another cetacean hot-spot: the South coast of Sri Lanka, off Mirissa, in December and April, is possibly one of the best places and times to spot Blue Whales in the world, where they are presumably in migration from their feeding grounds off Trincomalee to the feeding grounds in the Arabian Sea. The narrow continental shelf in this area means you can see the largest animal alive in the world today even while your boat is in sight of land!
The harbour at Mirissa has become the most popular starting point for whale watching excursions, mainly undertaken in medium sized fishing trawlers the excursions last anything from 2 hours to 7 hours depending on sightings of whales in the deep ocean. Whale watching is possible in these areas and the rest of the west and north west coast from November to March (avoiding the monsoon, where the oceans are too rough) and off Trincomalee and from the east coast from June to September.