Interesting---two spikes and pink. I've had two spiked flowers but they were always white. I once had the long narrow leaved variety, called Aponogeton guilotii, and it produced five-spiked flowers that were self-sterile. Your flowers ought to be self-fertile. Brush the pollen around on the flower with a small paint brush---the kind that is used for watercolors---and you should get a batch of seeds.