At the same time, the boat begins to move. So we can bring the same principle to the electromagnetic environment, that is, any space that carries electromagnetic waves: near-Earth space or outer space.
In your acoustic demo, the waves are traveling through mass and causing the mass to move, which propels the boat. In essence, it is a propeller with no moving parts. However, your EM version creates standing waves in empty (devoid of mass) space. How is that the same? I suppose your goal is to use EM to generate momentum, right? Has that ever been demonstrated before?