One of the most valuable certifications for adventure travel diving is Enriched Air Nitrox. Using Nitrox allows for longer bottom times and shorter surface intervals, which is crucial when you are doing multiple dives a day on a liveaboard. It also reduces fatigue, keeping you fresh for the evening festivities. We consider this a "must-have" for any serious travel diver. https://depthfindersscuba.com/travel/