Recent excavations at the ancient Maya minor center of Tutu Uitz Na in the Belize River Valley revealed an especially large—about 20 million shells—Middle Preclassic (900–300 BC) shell deposit underlying the plaza. Although marine shell species make up a small percentage of the assemblage, most shells are Pachychilus spp., a common freshwater snail known in the southern Maya Lowlands as jute. This report describes the architectural context and assemblage of the deposit and compares it to similar examples in the region. We propose that the Tutu Uitz Na deposit provides one of the earliest examples of depictions of the Maya primordial sea in an architectural context.