Michael Dunker\/Getty<\/cite><\/p>\n Onboard Obsession<\/strong> is a new series that explores the can’t-miss highlights of the best-loved cruises\u2014from the shore excursions to book to the spa treatments too relaxing to pass up.<\/em><\/p>\n As soon as my head dips beneath the warm waters of Indonesia\u2019s Bunaken National Marine Park<\/a>, I hear a mysterious tick-ticking, pop-popping sound that I haven\u2019t experienced before while snorkeling<\/a>. I quickly kick my flippers to rise. When my ears breach the surface, I hear a Lindblad Expedition<\/a> leader explaining to some fellow passengers of the National Geographic Resolution<\/em> that the faint sounds are signs of an extremely healthy coral.<\/a><\/p>\n I\u2019m on a 12-day journey from Vietnam<\/a> to Palau aboard the 138-passenger Resolution<\/em>, purpose-built to access waterways that would otherwise be impossible without dynamic positioning technology<\/a>, an X-bow construction, and a team of expedition leaders who negotiate \u201cdockings\u201d like this one, floating within a protected marine reserve with no other vessels in sight.<\/p>\n I dive again beneath the surface to the undersea equivalent of Tokyo\u2019s Shibuya Crossing<\/a>. Several green and hawksbill turtles are darting in and out of a vibrant coral cliff with seemingly millions of species, from sculpins to sun coral and everything in between. I strain my eyes and urge my brain to take in every detail and somehow lodge each scene into my memory bank. Often I repeat characteristics of sea life to myself while snorkeling<\/a> so that I can later identify the species back on board, with help from the expedition team and dedicated science center. One kick after another I spot a fish that I never thought I would see outside of a nature documentary: to the left are clownfish in their bubble-tip anemone homes, plus a lionfish, a porcupinefish, an octopus, a school of thousands of Niger triggerfish fluttering their fins like butterflies.<\/p>\n After what feels like hours of playing a marine version of Where\u2019s Waldo, I realize that I have drifted away from the group. I decide to turn and float on my back before catching up in one last-ditch effort to take everything in. The sun-soaked, tropical scene feels like slow motion suddenly, disorienting me in a way that I haven\u2019t felt since I was a child.<\/p>\n