That’s two different things. Muffled can be you’re recording from your laptop microphone by mistake or you have your directional microphone turned around. As a fuzzy rule with most microphones you talk into the company name.
Here’s a scratch test I shot.
Underwater is processing. Something is “helping you” with your sound. That’s harder. Windows could be doing echo cancellation or noise reduction, That Skype program you left running by accident can do that and any other chat app and some games.
It’s a little harder to get both. If you have very bad background noise, environment processing can give you muffled like talking into flannel. That’s right before it gives up and starts passing noise instead of suppressing it.
I’m not beating up on environment suppression. That’s what gives you the ability to chat while walking down the street holding your phone at chest level. However, nobody is going to pay entertainment money for that kind of sound.