We have a three years old feature request and an year-old pull request to implement it.
Can we use this code?
If yes, here you can find a slightly improved version (NPC will resurface when breathing level below 1/2).
If not, which behaviour would be correct?
An additional question: should combat AI use water breathing spells?
It seems vanilla Morrowind AI does not use it (include potions), and theoretically NPC can dive too deep (he will not have enough time to resurface).
AI: Resurface to breathe
Re: AI: Resurface to breathe
Implemented in a new AiBreathe AI package in this commit.