This datapack adds working dive helmets to minecraft. Drowneds have a chance of spawning holding one of these like a nautilus shell, and also have a chance of dropping it. When worn, the helmet will give you water breathing. Just be careful not to place it. If you place the dive helmet on the ground, it won't give you water breathing when you pick it back up. No resourcepack required. Java edition only.

Update 2!
Name a villager CaptainNemo and he will turn into a custom villager. If you place your dive helmet on the ground and pick it back up, you can trade the broken helmet for a new one. You can also trade a conduit and 10 emeralds for a helmet.