El Nido's Tour B itinerary threads through the Bacuit Archipelago's northern quadrant, a cluster of limestone islets shaped by 250 million years of tectonic uplift and karst erosion. Cathedral Cave on Pinagbuyutan Island holds the route's signature chambers — travertine columns and ceiling vaults carved by freshwater seepage during Pleistocene sea-level swings. Spanish chroniclers documented the cave network in 1623, noting Cuyonon fisherfolk who used the caverns as monsoon shelters and copra stores. Cudugnon Cave, a smaller pocket on Cudugnon Island, yielded pottery shards and burial jars during a 1965 National Museum excavation, evidence of pre-colonial habitation spanning 3,000 years. Snake Island earned its designation from the S-shaped sandbar that connects the main outcrop to a forested rise at low tide — a phenomenon driven by reversing longshore drift and the archipelago's semidiurnal tidal cycle. The sandbar disappears entirely during spring tides, reappearing as a 400-metre ribbon of crushed coral and shell hash when neap conditions prevail. Entalula Island's crescent beach, framed by overhanging pandanus and ironwood, served as a loading point for the timber trade in the early 20th century; rusted barge rings still protrude from basalt boulders at the northern end. Pinagbuyutan's vertical cliffs rise 180 metres, a nesting site for glossy swiftlets whose edible nests were harvested under Spanish monopoly licenses until 1898. Tour B El Nido package itineraries depart daily from the town beach, covering five sites across six to seven hours depending on swell conditions and group size. Shared bancas — outrigger vessels powered by Yamaha or Honda engines — carry 10 to 15 passengers alongside guides trained in basic navigation and reef identification. The route favors calmer northeast monsoon months, when visibility inside Cathedral Cave reaches 15 metres and sandbar exposure at Snake Island extends past midday. Provincial conservation ordinances limit daily visitation to 12 boats per site, a regulation enforced since 2019 to prevent anchor damage to seagrass beds surrounding Entalula and Cudugnon. The 400-peso eco-tourism development fee, valid for 10 days across all four standard island-hopping circuits, funds mooring buoy installation and waste collection at high-traffic beaches. Operators provision lunch buffets — grilled bangus, pancit, tropical fruit — served on beach mats at Entalula's designated picnic zone, a flat clearing behind the primary reef crest.