If so, how did they deal with breathing underwater and the crushing pressure? I’m trying to get a young Thor and Loki there in a fanfiction story, and I am reluctant to just go with ‘magic’. It seems like such a cop out, so I wondered how Marvel’s writers had dealt with the problem, and can’t find anything online.
Any facts from the comics or any ideas in general would be welcome!
Well, my husband showed me a cartoon (Batman Beyond?) wherein Batman went and visited Aquaman via a lot of Batpliances. It was a charming little episode, actually.
I don’t know if they’ve ever been but they are magic. There’s also the handwave I read about Asgardians having denser bone and muscle than flatscans.
The Fantastic Four have visited a few times. IIRC, when their sub was wrecked, Sue Richards’ force field kept them alive.
Reed Richards invented some breathing pills in Fantastic Four #27.
Alpha Flight and the Avengers went to Deluvia (an undersea colony of Atlantis populated by loyalists to Namor, at a time when Namor wasn’t welcome in Atlantis itself) in Alpha Flight #40, which I figure is close enough.
The Defenders went there twice, the first time (issues 7 and 8) with little more than glass bubble helmets. This included Hawkeye, the guy with no real superpowers. This is one of the first Marvel comics I ever read, I was 12 at the time, and even I thought Steve Englehart skimped on the details.
The Fantastic Four (who go to Atlantis every couple of years) all have powers that protect them from pressure. Johnny, when flamed on, is made of plasma, not flesh and bone and he usually has some gimmick (like oxy-gum or an oxygen net) that lets him flame on underwater.
Batman’s DC. Get your universes straight 
Asgardians don’t breathe, do they? They travel through space unprotected and without an air supply.
Like Batman, Thor can do most anything if he’s prepared. If he takes a deep enough breath, he can hold it for hours and operate efficiently in space. And I don’t think he likes spacesuits; it wouldn’t surprise me if the standard Stark Enterprises number doesn’t hold up to the force of Mjolnir coming back to his hand after he hurls it, so he just says fuck it.
This.
I don’t know about Loki, but I’m sure Thor’s way less crushable than Namor. He just needs one of those bubble helmets (but in reverse) that the Atlanteans used to use when invading the surface world and he’s set.
Going back to Loki, everything he does is via magic, so it’s no cop out at all for him to use magic here.
Stephen Strange visited the ocean floor alongside Reed in that issue, sort of.
Thanks everyone! I knew I could count on Dopers to know! I’m going to go looking for a few of these comics, and I may even watch the Batman episode for fun! I haven’t made up my mind about the breathing issue, but after being reminded that Asgardians are tougher than humans, I’m just going to ignore the pressure issue like the comics writers generally have.
Wolverine visits during Civil War. He’s in a bulky diving suit.
