Marsh or Swamp?

This is actually a question that came up when I was investigating my backyard. Around thirty to forty feet from the back door is the beginning of a wooded area which is very often inundated with water due to the heavy rain we will sometimes get. Where I live we do have both very nearby. So, what is what?

What is a swamp?

swamp  (swŏmp)
An area of low-lying wet or seasonally flooded land, often having trees and dense shrubs or thickets.
The American Heritage® Science Dictionary

This would be what I have in my backyard (though it's seasonally flooded). The major point here is the presence of trees where the trees are sometimes inundated with water. Also, swamps are always purely fresh water and will never be inundated with salt water. This would be where you would find creatures like alligators.

A swamp with iconic "cypress knees"

What is a marsh?

marsh  (märsh)
An area of low-lying wetland in which the level of water is generally shallow and often fluctuating. The water may be either standing or slow-moving. The water in a marsh is also more or less neutral or alkaline, in contrast to the water in a bog, which is acidic. The environment of a marsh is in general well-oxygenated and nutrient-rich and allows a great variety of organisms to flourish. In contrast to a swamp, in which there is an abundance of woody plants, the plants in a marsh are mostly herbaceous. Reeds and rushes dominate the vegetation of marshes. See also salt marsh.
The American Heritage® Science Dictionary

Due to where I live, when I hear the work "marsh" I usually think of a salt marsh. However, marshes are not necessarily salty. The major point is the lack of trees. In a salt marsh trees are occasionally seen, but they grow on areas of higher ground on small islands. The salt marsh is an iconic part of the Georgia coastline and it fills the spaces between our barrier islands and the mainland. Marsh grass (Spartina) is a very prominent plant, covering vast areas that are interspersed with tidal rivers and streams. Prominent animals include crabs, sea birds, and oysters.

Salt marsh at high tide, with healthy Spartina

Definitions are from Dictionary.com. Images used are from Flickr.com under creative commons licenses: one, two