Whale and Dolphin watching
This has been most popular attraction among the tourists who visit sri lanka. since the year 2010 and still Sri Lanka operating whale watching trips based on Mirissa Harbour from october to May. Whales are spotted few nautical miles off mirissa harbour. The boats with passengers depart from the harbour by 7am. Hence you must be there at least before 15 minutes and you just need to remember your passport number to provide for security reasons(for locals it's NIC number).