We present the lead isotopic composition of ceramic fragments from the Kyrenia shipwreck (Cyprus), selected from three chemical groups related to the Rhodes and Alimos regions (Greece). Fragments of the lead sheathing covering the ship’s hull and biogenic material formed on some of the ceramic sherds, were analyzed along with sherds from the Rhodes and Alimos source areas for comparison. The objective of this paper was to evaluate the impact of the seawater environment on the isotopic signature of the ceramics, and on our ability to use lead isotopes to source ceramics recovered from seawater. The results showed that the lead isotopic composition of the shipwreck ceramics was modified by its prolonged proximity to the lead hull sheathing. The lead signature of filtering marine organisms encrusted on the ceramics provided support for this hypothesis.