For making pool volleyball, there are a number of materials that you can use, like nylon ropes, vinyl ropes, or polyester.
However, when making the material selection, we would advise that you keep in mind that the net is going to get wet during your volleyball sessions. So, it is best to use materials that are resistant to water that would not get damaged easily. Doing so will ensure that the nets last longer, and you don’t need to change them frequently.