Why are there duplicates in the following words 游游泳, 化化妆, 散散步, ..., etc?
Reduplication of a verb  

'with AA Pattern' indicates the action occur in a slight degree, brief time period or casual manner

Examples:

看- to look; 看看- to look briefly

走- to walk; 走走- to walk briefly 

敲- to knock; 敲敲- to knock slightly

嘗- to taste; 嘗嘗- to slightly taste 

Another form of Reduplication 'with A一A Pattern' indicates the action occur in a single instance, slight degree, brief time period or casual manner

Examples:

看- to look; 看一看- take a look/ to look briefly

走- to walk; 走一走- take a walk/ to walk briefly 

敲- to knock; 敲一敲- knock once/ to knock slightly

嘗- to taste; 嘗一嘗- taste once/ to slightly taste 

For verbs that are made up of a two characters like  游泳, 散步, you only need to reduplicate the first character. 

游泳- to swim; 游游泳- to swim casually (or briefly)

散步- to take a walk; 散散步- to talk a walk casually (or briefly)