The park is home to a shallow fringing reef which sits only a few meters beneath the surface, thus making it a perfect area for snorkelling and scuba diving. The main reef itself is a typical fringing coral reef with a shallow crest and a sheltered lagoon and only has an average depth of fewer than 2 meters below the surface. The reef begins at the fishing harbour and extends south for around 4 kilometres.
Quite simply, the reason people visit Hikkaduwa National Park is for the excellent snorkelling and scuba diving the reef provides. There are around 60 species of hard coral along with over 170 species of tropical reef fish in the fringing reef at Hikkaduwa National Park. Visitors to the reef can find large stands of cabbage-type Montipora corals and small stands of branching Acropora corals. There is also an abundance of boulder type and encrusting corals. In terms of fish, divers can expect to see angelfish, butterflyfish, parrotfish, snapper, wrasses, Trevelyan, and various species of the sea turtle.