Similajau is the main reason anyone without a gas industry connection visits Bintulu. The park protects a long strip of coastline — rainforest right down to the beach — along the South China Sea. It's a genuine national park rather than a landscaped tourist attraction: trails are marked but not manicured, wildlife sightings are real rather than staged, and outside of Malaysian school holidays you may have the beaches largely to yourself.
The trail network runs roughly parallel to the coast. The main path follows the shore from park headquarters, crossing rivers by hand-pulled sampan, and passing through primary forest that holds gibbons, hornbills, saltwater crocodiles in the river mouths, and occasional dolphins offshore. The beach itself is long and clean, though swimming is not advisable near the river mouths. Chalets and a hostel are available at headquarters; book through the Sarawak Forestry Corporation well in advance for weekends.