What is the difference between marsh, swamp, and bog?

These three words are quite similar to me and I often get them confused in English.

Please help me to understand their differences.


I am a native user from New England. Here's my perspective:

Swamp = wetlands near ocean, river, or lake, in an area where it never gets cold enough for the water to freeze. I imagine Spanish moss, mangroves, and alligators.

Marsh = wetlands near the ocean only. In my mind, only in areas where it does get too cold for alligators to live. All the marshes I've seen are grassy habitats for certain wild birds and aquatic species, and are very wet; not as much muddy as the other two.

Bog = wetlands near inland fresh water only. Also in non-alligator country. Bogs can be small, shallow, muddy patches where turtles like to hang out, or deeper and larger and dangerous to walk into because the mud will suck you in. Bogs will freeze solid in winter.

Only "bog" and "swamp" are used to convey different meanings, particularly with verbification, e.g.:

The meeting got bogged down by nitpicking naysayers on both sides of the controversy, so there was no final decision, and the vote was tabled til next month.

He was already behind on several deadlines and could not take on yet another project. When asked if he could help out, he said, "No can do, sorry. I'm totally swamped."

And as tchrist mentioned, there is variation in native usage, so you might get a different answer from everyone.

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