I enchanted a Netherite Helmet with Aqua Affinity I and (in survival mode) mined blocks underwater and the aqua affinity very rarely worked and would often stop while still mining the same block and it was mostly mining with the speed of normal underwater mining. To clarify i was wearing the helmet
I do not know what version number it it but it is the current Bedrock Edition on Xbox One so i will put 1.16.1
Edit: Fixed "Aqua Affinity III" in this post and a couple typos I made