A support assembly for a mooring line of a floating vessel comprises a trunnion block which is pivotally supported on the vessel and a stopper block to which the mooring line is releasably secured. One of the trunnion block and the stopper block comprises a convex surface and the other of the trunnion block and the stopper block comprises a concave surface. In operation, the convex surface engages the concave surface to thereby pivotally support the stopper block on the trunnion block.