Naturally occurring protoplasts were observed in a culture of Ulva lacinulata collected two years prior. This strain has been cultivated under laboratory conditions and after many attempts at induction of reproduction, no method described in the literature showed any success. Moreover, degradation is known to occur often in this species, and during one of these occurrences, we closely observed the thalli, the tissue degradation, and cells that were found being released into the water. We confirmed that these cells were naturally occurring protoplasts and found that the initial partially degraded thalli could recover and grow after the natural production and release of protoplasts. Our observations of natural protoplast production during tissue degradation in U. lacinulata close an important knowledge gap in understanding this species’ reproductive cycle, which is one of the most cultivated Ulva spp. Additionally, the production of natural protoplasts can potentially be exploited to improve the efficiency of Ulva cultivation methods in the future.