The fringing reef that protects Unawatuna Bay also makes for decent snorkelling straight from the beach. The coral is not pristine — it was damaged by the 2004 tsunami and has recovered unevenly — but the fish life is good, and on a calm day with clear water you can see parrotfish, wrasse, surgeonfish, and lionfish within easy snorkelling distance of shore. Mask and snorkel sets are available for rent from several operators along the beach for a few hundred rupees.
The best visibility is from November to April, during the dry season, when the northeast monsoon keeps the water calm. Outside this window the current can strengthen and visibility drops. For deeper dives and the nearby shipwrecks, the dive operators based along the beach road offer guided trips; the Rangoon wreck, lying in about 18 metres of water just outside the bay, is the most popular dive site.