All of the slow mo sounds are recreations. In fact I’m pretty sure they use that same sloshy sound clip in about half their videos.

Smarter Every Day did a video about this. I think it’s this one: https://youtu.be/aO7yzmc3ykw

They're all recreations. Look up Foley if you want to be disappointed in almost everything you've heard on a TV show or movie. For example, elephants don't make loud thudding noises when they walk -- that's all made up.