quicksand ، quagmire ، swamp

I'm sure by now that you've looked them up. What's your feeling of their relative meanings?

Some random observations:

"swamp" is by a long way the most common term of those listed.
"quagmire" is often figurative (probably more often figurative than literal, I would guess).
"quicksand" is a more specific word than "swamp", particularly emphasising the danger of being sucked in and trapped.
I don't know "sinking bog". I wonder whether it may be US-specific.

GPYI don't know "sinking bog". I wonder whether it may be US-specific.

I live in the U.S. Never heard of such a thing. I was wondering if it might be England-specific.

CJ

When I hear 'sinking bog', Scotland springs to mind.

fivejedjonWhen I hear 'sinking bog', Scotland springs to mind.

Hopefully, not the whole country.

sunny1233. sinking bog

You don't need the word sinking, there.

Anonymous sunny1233. sinking bogYou don't need the word sinking, there.

It seems evident from Google results that "sinking bog" is a known term, just an uncommon one that no one here (so far) is familiar with. "sinking" presumably means that you sink into it, like quicksand.

AnonymousYou don't need the word sinking, there.

I agree with GPY that this is familiar as is. Just as "swimming pool" survives without "swimming", both are OK.

GPY Anonymous sunny1233. sinking bogYou don't need the word sinking, there.It seems evident from Google results that "sinking bog" is a known term, just an uncommon one that no one here (so far) is familiar with. "sinking" presumably means that you sink into it, like quicksand.

Maybe it's a regional thing? It's certainly not universal.