An important area of nanotechnology is the development of experimental procedures for the synthesis of nanoparticles that are biologically inspired. New environmentally friendly "green" synthesis techniques are being developed to address the rising demand for commercial nanoparticles. In this study, Ulva fasciata sea weed extract was used to synthesize stable silver nanoparticles (AgNPs). The synthesis of AgNPs and the reduction of Ag ions in the media are both observed using a UV-Vis spectrometer. AgNPs that have been synthesized have had their morphology studied using XRD and SEM. The peaks in the XRD pattern correspond to the metallic silver's face-centered-cubic (FCC) structure. Silver nanoparticles are discovered to have an average grain size of 6.35 nm. TGA/DTA results showed that desorption of chemisorbed water was associated with exothermic reaction and weight loss. The carbonyl, hydroxyl, amine, and protein functional groups that form a layer atop AgNPs and stabilize them in a medium were identified using FTIR. Moreover, the antibacterial activity of silver nanoparticles was done and the results were phenomenal with large inhibition zones.