The van eases out of Puerto Princesa’s low-rise bustle and the road narrows into a corridor of coconut palms and weathered limestone. By the time the sea appears, it is not a postcard blue but a living color — green where mangroves bite into the shoreline, and a deeper, oceanic blue beyond. On day two this slow corridor ends at Sabang, where small bancas wait to ferry you into the mouth of the Puerto Princesa Underground River. The river doesn’t so much reveal itself as insist on attention: a dark throat carved into Pleistocene limestone, currents that nudge the boat forward, and chambers where sunlight spills through unseen holes to paint stalactites in amber.