I found imagining the actual metaphor of tarpit enlightening - it looks like a nice healthy pool of water but turns out to be sticky and impossible to get out of. Under that attractive surface are all the corpses of everyone else who charged in and got stuck.

So it’s exactly like you say: you keep your distance and you look for evidence.

I do think the point of the metaphor is that sometimes a tarpit is just what it is. I.e. there is no value under that shiny surface and you’re only getting stuck staring at it.