So, I'm in Vault 3, and I've killed all the Fiends, freed the people in the cage, and unlocked the doos to the underwater storerooms. However, I keep drowning when I try to swim down there and back. I've made it to the rooms, so, I know what kind of stuff is in there, but I can't get it and get out. I read in another thread about some king of diving gear you can get. It is supposedly somewhere in this vault, in the same room with an injured NCR soldier. I have been all through this place, and haven't found anything like that. No NCR soldier, no diving gear. Can somebody clue me in here, please?

You can get a water breathing device from some Boomer quests at Nellis Airforce Base, that's probably what they mentioned. And it seems that it's needed to retrieve the items in those rooms.

That is the only underwater breathing equipment that is in the game I found. Many mods have armor that breath in water however.

Ah, okay. Thanks guys, appreciate the help.

I just went back to McCarran, and Col. Hsu thanked me for saving Ranger Anders. I never saw Anders anywhere in Vault 3. Was he in the cage with the kidnapped caravan people?

Nope, he's to your left as you enter the living quarters (same area/cell as the captives). Follow the hallway to your left as you enter the living quarters, you'll come across a dead Fiend (you'll hear him/her die when you enter) and traps. Behind all this you'll find Anders.

Then it must be a glitch or something, because I never saw or spoke to Ranger Anders, but according to Col. Hsu, I rescued him.