I should not see the sandy hourglass run,But I should think of shallows and of flatsAnd see my wealthy Andrew docked in sand
Sandy hourglass refers to an hourglass, which was used to tell the passing of time. According to Salarino (talking to Antonio), were he in Antonio's position, something as little as the sand in the hourglass would cause him to dread that a ship had been wrecked on the sand.