An inflatable structure includes a top end cap, a bottom end cap, a bladder, a nozzle, a loop, and a first tether. The bladder is attached to the top and bottom end caps and is configured to hold pressurized fluid therebetween. The nozzle is configured to allow fluid to enter and exit the bladder. The loop is attached to one of the top and bottom end caps. A tether is disposed within the bladder, coupled to the other one of the top and bottom end caps, and extends through the at least one loop. The top end cap assumes a first position when the bladder is inflated. When the top end cap is adjusted from the first position to a second position, the first tether is configured to maintain the top end cap in the second position.