This paper offers the first mixed-methods evaluation of maritime operations by insurgencies. Maritime insurgency refers to coordinated campaigns by insurgents to influence their land campaign through smuggling, piracy, or maritime terrorism. This article identifies maritime smuggling as a causal mechanism that increases insurgency duration by providing access to arms with greater control than non-maritime insurgencies. I use two approaches to demonstrate the plausibility of my argument. First, I identify 19 of 104 insurgencies since the end of the Cold War as maritime and fit a cross-country duration model. Second, I contrast the Liberation Tiger of Tamil Eelam and Naga insurgencies to explore the plausibility of maritime smuggling as a causal mechanism. I find maritime insurgencies are 80.7% less likely to end on a given day than an equivalent insurgency that does not use the water. The plausibility probe demonstrates the criticality of maritime smuggling to the resistance of the Liberation Tigers of Tamil Eelam in Sri Lanka. This mixed methods approach presents strong evidence that maritime smuggling contribute to increased insurgency duration.