An access device adapted and configured to be inserted through a natural biological orifice, and related surgical methods are provided. The access device includes a body, a nozzle means and means for delivering a pressurized flow of fluid to the nozzle means. The body is configured and dimensioned to be inserted through a natural bodily orifice and has proximal and distal end portions and defines at least one lumen therethrough to accommodate passage of one or more surgical instruments. The nozzle means is operatively associated with the body for directing pressurized fluid into the lumen to develop a pressure differential in an area within a region within the lumen to form a fluid seal around the one or more surgical instruments passing therethrough.