Semporna is Sabah's launch point for three very different underwater worlds: Sipadan's oceanic walls, Mabul's macro-rich reefs, and Kapalai's shallow sandy slopes and turtle-filled house reef. From a small mainland town you can reach Sipadan Island Park by speedboat, where controlled permits help protect one of Malaysia's most celebrated dive sites. Back closer to shore, day boats and island resorts deliver easy dives, critter hunting, and snorkeling over coral gardens. Add Tun Sakaran Marine Park for lagoon viewpoints, beach-hopping, and Bajau seafaring culture. Expect warm water around 28°C, visibility that can range from 10 m to 30 m, and currents on exposed walls that reward good buoyancy and situational awareness.