It is not uncommon for C. nuri to flower underwater in aquaria.
This is Cryptocoryne nuri nuri which is often found in soft acidic water. There is also another subspecies - Cryptocoryne nuri raubensis

biotope Pictures of the biotope of Cryptocoryne nurii. cultivars Albovena Pink Platinum Poseidon Rosen Maiden Silver Queen "Regina" Splendor emerse

flower locations SW Suwidji Wongso accessions Bintan Lingga Mersing N Johor Pahang Riau Sg Tersang Terengganu submersed