I can't seem to find a definitive answer, but it seems like Cricket only requires the arm to completely straight when bowled and it cannot be underarm. This opens up the possibility of someone bowling a "submarine pitch" as It's essentially just sidearm while bent at the waist so that the shoulders line up with the arm. All you would need is your arm to be completely straight. You'd also be able to more accurately bowl a seam ball and achieve more spin being closer to the ground.
Is this legal? Or is there a law that I've overlooked governing this?