The theory being proposed and considered here is fairly simple, based on several basic key concepts from psychology and anthropology. Stated bluntly, my theory is this:
Since humans reason symbolically, and hide estrus, they must depend on symbols to substitute for biological mating cues. Given this context, anything, or anyone, can be interpreted as a sexual symbol by a given individual.
And what, may you ask, do I mean by a "sexual symbol"? For purposes of this discussion, I mean any object, person, situation, that evokes an erotic response from the one perceiving the above as erotic. Sexual symbols can be clothing, activities, situations, different types of people.
Perhaps the individual in question finds leather erotic. Maybe fat busty girls is his / her thing. I once new a man that found blond women who were at least 3 inches taller than himself irresistible. By the way, this was not a short man, the women he liked were tall! I personally have a thing for petite red-heads. I am 5' 7" tall. I speak of girls who are approximately 4' 9" to 5' 3". Every once in a while, I see a girl around 5' exactly, red hair, very petite and well proportioned, as memorable and devastating. I can see a woman like this in a crowd, never meet her, and she'll stay in my memory for life, such is the power of this particular symbol to me.
In the case of WAM, the sexual symbols are situations and substances. The situations involve getting messy in some way shape or form, and the substances are always wet, hence the name of the genre: Wet And Messy sex fetish. This is a rather broad umbrella for a set of categories that include anything from food to mud to just plain water.
For the fetishist, sexual images can take the form or any portion of a person's anatomy, clothing, a situation involving a person or thing, anything you could possibly imagine. Most psychology texts include references to clothing and non-sexual body parts, such as dresses and feet. In reality, fetishism includes a bewildering array of potential sexual symbols. These fetishes include:
One of the people in Wamfanmail has an amazing collection of Levi's 501 jeans.
The possibilities stretch endlessly.
Pick a topic, and I'll bet you can find a fetish devoted to it.