You should try collecting pollen from different anubias (if you have more than one). It could become a cool project to get more anubias the hard way. Not sure how difficult it actually is, though. Makes me want to try, actually.
I thought they only flowered above water. Just goes to show how much I know, and how much I have left to learn. I didn't even think that it would flower underwater. The though of underwater flowers is just kinda weird, and didn't even trigger a double take on the picture.
No flowering plants naturally flower underwater. Flowers are designed to be pollinated by insects. All flowering aquatic plants have flowers that are on or above the surface of the water. Any plant that flowers under water is confused for some reason.