Minetest mod to disable drowning, so you can swim and live underwater forever.
Air/breathing limits are a timer that prevents thinking, planning and generally having fun. Underwater effectively becomes a desert that people avoid where possible. Water should be interesting, not gameplay mud.
Minetest already does underwater a lot better than Minecraft traditionally has. You're not blind and mining speed is not reduced. I think underwater would be more interesting if so many people did not grow up with Minecraft teaching them that it's punishment.
It works
yeah, it just works, there is no argument. You could happily enjoy water life all you wanted.