Selingan is famous as a nesting site for Green Sea Turtles, and that's what we were there to see. After a short museum exhibition and video, we were sat in the island's main house, along with all the other visitors, and waited for the turtles to start landing.
The beaches on Selingan are strictly off limits to guests between the hours of 6pm and 6am, to ensure that nesting turtles are not disturbed. Park rangers wander the beaches at night recording nesting sites and harvesting eggs to transplant into a sanctuary. Each night the rangers select only one nesting female for the island's visitors to observe. Once the chosen female is settled and well into her egg laying, the visitors are escorted from their 'holding pen' out to the turtle to observe the process. Lights and flashes are prohibited during this time so as not to disturb the female.
Once she has finished and is covering her nest, the lights are turned on for a few quick photos, and then she is left to it as her eggs are transplanted to a sanctuary on the island.
From top to bottom: waiting around for the turtles to land; a nesting female illuminated by someone else's focusing beam; the female having finished nesting, and the park ranger who was collecting her eggs; portrait of a green sea turtle; turtle egg sanctuary; artificial nest for the eggs.
PS: Green sea turtles are fascinating creatures. Their name comes from the olive-green coloration on their shoulders, and the male/female ratio of a nest depends entirely on the temperature of the nest during incubation. Salt glands behind the turtles' eyes secrete fluid, making the turtle look like she is crying during nesting. For more information visit the wiki on green sea turtles.