Is it expected of heterosexual men to not look lustfully at bikini-clad women in beaches? I have noticed that everyone seems to be behaving as matter-of-factly, whereas I make a bit of conscious effort to not notice the semi-nude women.

I feel that such a scene is arousing, to say the least. Let me put some context. We all know that people often purchase lingerie to spice up their sex lives. This is because female body looks very seductive when scantily clad. So, the same woman would also look very enticing in a bikini.

In general, when women wear "bold" garments like short skirts, or cleavage exposing tops, is it expected of men to look as if it the same as a woman wearing less bold clothing?

EDIT:
Some clarifications: Since most answers steered off the subject of my question, here are some clarifications:

My question is, do most people not notice?

Let me give an example. Say, we live in a society where women generally wear clothes that fully cover their body. In this scenario, even when a woman wears a dress, people around will "notice". But in our times, in most parts of the world, most people wouldn't notice such attire.

What I want to know is do people notice a woman wearing bikini?

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In my personal experience, I have never felt uncomfortable around women who wear less bold garments. If it is normal for people to not be uncomfortable in the presence of scantily clad women, maybe I have to work on myself (I was raised in a pretty conservative/traditional family).