I'd like to create the textures of sand and water in this photo I took at the beach
You have three distinct layers there. From bottom to top, layered like a painting:

The opaque sand layer;
the shadows of the waves;
the waves themselves.

If wanted, you can have an underpainting that shines through.
Now, going back reversely:

As for the layer of the waves, the most pleasing effect would be for it to be translucent, so I suggest glazing this last layer using oil paint.

I find that the shadows of the waves - the second layer - already resemble water colour, and, as this a perfectly fine (although outmoded) underground for an oil layer, it would be a practical choice, as well.
Since you might be working with oils, the medium you're working on should be properly prepared, using gesso or skin glue (with chalk).

The layer of sand can be achieved in a multitude of ways, but, if you want to have some texture, it could be nice to add real (very fine) sand to the preparation medium of your choice, to make it feel a bit more organic.


Something important to take into consideration (which you hinted at with your suggestion to use 'stamps'), is that the second and third layer are - naturally - quite similar.
If you'd print the photograph to scale, you could use carbon paper to trace the wave lines. This will give a much better and convincing idea of the interference than when you approximate these by hand. It will also give you a good blueprint for the second wave layer.