The UN Convention on the Law of the Sea (UNCLOS), adopted in 1994, establishes international maritime boundaries that are measured from the “normal baseline” where the ocean meets the coast. However, UNCLOS does not account for changes in the normal baseline that are expected to occur as a result of climate change-induced sea level rise. These uncertainties leave room for maritime territorial disputes that threaten the political and economic resources of small island developing states (SIDS) and developing coastal nations. Here, we discuss the impacts of sea level rise on maritime boundaries with a focus on equity for SIDS and developing coastal nations. These nations, though they contribute the least to climate change, experience its effects most drastically and are the least equipped to adapt. To safeguard against the inequities that are expected to result from rising sea levels, we recommend a science-informed, diplomatic effort to address this issue: that the International Maritime Organization introduce an international convention to establish static maritime baselines. This approach would freeze maritime boundaries, allowing all island and coastal nations to retain their existing oceanic zones and entitlements. Establishing a static baselines promises to mitigate the disproportionate effects of climate change on SIDS and represents a necessary step in the push for international equity in the face of climate change.