Well, without the Heightfield node trick, you could also try:

Download and use the Noise turbulence melscript from Highend,
or the channel-noise mel from Dirk Baluch's site on your nurbs plane geometry to get a pseudo-wave look.

You could also try using blend-shapes to get your wavy look by using the Paint tool to deform your geometry, then making that a blendshape for other tweaks over time and key the changes to get your wavy geometry.

Or, similarly, you could just use the Paint tool and just key your vertice positions over time.


Then, make the surface LIVE. (check the docs regarding that)

Then "Paint" particles onto your LIVE geometry, then do your instancing etc.
and they "should" then follow the deforming geometry.

Lemme know if any of that helped