"The study has demonstrated that decaying seagrass accumulated along the shores is a particularly good source of cellulose and cellulose nanocrystals (CNCs). The FTIR spectra indicated the presence of O-H and C-H bonds in both the cellulose and CNCs obtained from the seagrass biomass. The Micro-Raman spectra showed maximum peaks at 1277 cm-1 for cellulose and at 1108 cm-1 for CNCs. The XRD spectra of cellulose confirmed its crystallinity, with a maximum peak for both cellulose and CNCs at 22°. The thermal stability of cellulose was lower than that of CNCs, where the latter showed thermal stability ranging between 110-250 °C. Overall, the cellulose and CNCs obtained showed good crystallinity and thermal stability. The particle size of the CNCs was recorded to be 253.2 nm. Also, they have a large surface area to volume ratio, which contributes to their high strength and stiffness. Thus, the cellulose and CNCs produced from decaying seagrass impart economic value to waste biomass, which can be a step towards the implementation of the wealth from the waste concept."