Actors no longer try to speak underwater (#3851)
From the video (correct me if I'm wrong), it seems like you cannot speak to NPCs underwater anymore, no matter what?
If so, I used that vanilla "bug" in a mod of mine (Desert Region 2, in fact) and as a precautionary measure, I made a compatibility patch. Because there is a main quest where you need to speak to a drowning NPC to progress and if that bug/feature has been disabled, you would not be able to progress.
But there may be more mods out there which also require you to speak to underwater NPCs or creatures, so that may be a cause for concern.