Here's why:

* Surface water waves are transverse waves. This means the particles move perpendicular to the direction the wave travels. So, they do move back and forth.

* However, they also move in a circular path. This is because the wave energy causes the water particles to move in a circular motion, with the diameter of the circle decreasing with depth.

Therefore, the particles in a surface water wave move both back and forth and in a circular path.