Fetish is strong sexual desire or arousal caused by a physical object. Getting turned on by a hot girl in a bikini or a hot guy in a Speedo isn't a fetish. If you get turned on by a bikini or speedo that no one is wearing, or you can't get turned on unless a girl is wearing a bikini or a guy is wearing a speedo - that's a fetish.
Sorry... but that is not current usage.
Fetish is a term early shrinks lifted from anthropology, referring to an object of particularly symbolic ritual import.
In psychology, it was used to characterize certain behaviors as sexually deviant, by suggesting that practitioners had an unhealthy and obsessive fixation on a particular artifact or material , and were incapable of sexual gratification without their fetish being involved.
This was absolutely unsupported hogwash, that never reflected actual human sexuality and currently is in the same realm of disabused nonsense as women suffering from "penis envy" and "hysteria".
Actual human sexuality features lots of behaviors in which particular articles, materials, colors, scents and even circumstances become conflated in the human psyche with arousal... But their absence does not prevent arousal since people can fantasize about them.
Basically... the entire idea of fetishism as you describe it has been debunked... ALL human beings develop conditioned responses to stimuli that they find particularly arousing.
It is simply those that vary dramatically from the most common that draw attention... but whether you are into S&M, or girls in school uniforms, or plain ol garden variety naked women is simply a matter of difference scenarios, and dos not necessarily indicate any kind of pathology.
They are all just different manifestations of the exact same sexualization process.
Today... the term fetish has become, most commonly, the term used to describe any kind of fascination with anything other than primary sexual charcateristics that seems linked to sexual expression and gratification.
Pretty much anything that is not vanilla sex, involves something that can be called a fetish.
From armpit hair, to leather corsets and whips. Hell, even a fixation on gigantic boobs, is considered a form of fetishistic fixation, if its something that helps get you off.
Aside from a minority of hopelessly clueless Freudians and Jungians, no one uses the term strictly as originally coined...
And it is not even considered deviant anymore. Everyone has fetishes. Even Missionary position, if thats the thing that you fantasize about the most, can be a fetish.