Mirissa beach is popular for whale watching tours. There are several whale watching tours conducted by local companies. Usually, tours take place in the morning and in the afternoon. On average the tours take from 2 to 5 hours. If a whale wasn't spotted the companies give you a free tour.
There are different varieties of whales in Mirissa. They are sperm, humpback, blue, killer (orcas), and short fin whale.
Apart from whales, dolphins are common in Mirissa beach.
Mirissa beach also offers scuba and deep sea diving. There are also private boats tours conducted by the Sri Lanka Navy for short cruises to explore south of Sri Lanka.
Mirissa beach is also a good spot for relaxation in the warm sun.