Caves on carbonate islands are useful indicators of past sea level because cave formation is dependent on sea-level controlled freshwater lens position (flank margin caves), or form in direct contact with coastal processes (sea caves). Sea-level curves present a useful proxy for glacioeustatic and paleoclimate studies, so caves offer useful data. Once a flank margin cave is breached, it may be modified and eroded by waves. This overprinting leads to morphology similar to that of sea caves. While both indicate past sea level, they reveal differing information about the amount of denudation that has occurred to expose them (a paleoclimate indicator), so differentiation of these cave types is important. This study presents some of the first sea cave data from carbonate islands, and makes morphological comparisons between flank margin caves and sea caves from the Bahamas, California, and Maine. Using morphometric techniques, these caves can be distinctly identified.