I know that some catholic schools had pools even before V2, so of course people were swimming in them and this was seen as alright.

Does anyone know how they were required to dress or what the swim wear looked like? Were men, for example, allowed to swim shirtless and in very short shorts?

I am not embarrassed in posting this photo of myself, my sister and a friend
of the family who was an Altar Boy at the nearby Our Lady of the Lake Catholic
Church.
Photo taken at a pool near Crestline, Ca. in the Summer of 1952.

So modesty doesn't apply if you go swimming or to the beach? Were 17+ year olds allowed to dress like that as well?

Indeed, I've never understood the mindset that, if there's sand on the ground or it's a swimming pool, Catholic norms of modesty no longer apply.

I think it is a mistake to look at practices from the 1950s and say "well, that was before Vatican II, so that means it must be okay." There was already a lot of worldliness at that time and Catholic culture had already taken a huge beating. In my view, the existence of swimming pools at Catholic schools may be an indication of some backsliding, although if mixed bathing were not allowed at those pools, many of the concerns are mitigated. Also, they would be private, and private bathing segregated by sex can't be compared to public and/or mixed bathing.

It is my understanding that the Church has always condemned mixed bathing. Spain is a country that has a lot of beaches, but at least one of the prelates there, Cardinal Pla y Daniel, Archbishop of Toledo, stated in 1959:  "A special danger to morals is represented by public bathing at beaches...  Mixed bathing between men and women, which is nearly always a proximate occasion of sin and a scandal, must be avoided."

Apparently the bishops of Spain together published in 1958 a docuмent entitled "Norms of Christian Decency". I've been unable to find an English transcript of this docuмent, and only found reference to it in some news articles talking about some "extremist" Catholic/Carlist group that was calling for segregated beaches and used this docuмent to back up their position (cf. http://www.dailymail.co.uk/travel/travel_news/article-3154546/Extreme-Catholic-group-Pedro-Men-ndez-Avil-s-urges-beaches-segregated-sex-northern-Spain-sins-flesh-avoided.html)

The oft-quoted January 12, 1930, instruction of the Sacred Congregation of the Council, does not differentiate between whether there is sand on the ground or not.

I think it is worth recalling the grave scandal that was occasioned when bathing dresses started appearing in the mid-late 1800s and women would go as deep as ankle-deep water at the time. It shows you how far we've come, and I think it gives an indication of what attitudes were like for centuries.

I've studied a fair bit of Medieval life and culture and I've never found references to public bathing. There were lots of bath houses, but these were segregated and, again, it's private. Wealthier people bathed in private.  My impression is that on the whole, the culture of bathing was to get in and out relatively quickly, to get clean.  

I believe public beaches and swimming pools should be segregated by sex so that the people who use them are not tempted to sins of lust. The last time I went to a public beach I had to confess it as a mortal sin. It was stupid of me to go there but I did and I spent most of the time trying to not stare at half-naked women.

Half-naked women?  

More like 93% naked.  The last beach I visited had a lot of women who didn't even have their "glutimus maximus" completely covered.  

The same standards apply at a lot of these Concilliar World Youth Day get-togethers.

Swimming pools should not be mixed, and people should be dressed as decently as possible, especially women. As for open-air swimming pools, they should include a hedge, preventing people from outside to see the swimmers.

While your opinion is nice and all, the guy is asking about what people did back then not what they should do.

I know that some catholic schools had pools even before V2, so of course people were swimming in them and this was seen as alright.

Does anyone know how they were required to dress or what the swim wear looked like? Were men, for example, allowed to swim shirtless and in very short shorts?

At Fatima 1917, Our Blessed Mother said:

 "More souls go to Hell because of sins of the flesh than for any other reason. "
"Certain fashions will be introduced that will offend Our Lord very much. " "Woe to
women lacking in modesty".

Those fashions came into existence like overnight in 1920+-. Young women, called Flappers, started wearing mini-skirts, low cut tops, two piece bathing suits, and whoring around town. If you watch old movies on Youtube, you will see the fashions and the brainwashing by Hollywood. This immodesty did not happen in the 1960's, it goes back to 1920+-.

With regard to the beach, I have pictures of my grandfather in 1920-30's wearing what would be described today as Under Armor Boxerjock's. He looks ridiculous.

People can be convinced of anything.

Girl today: This is my underwear, I only let my "boyfriend" see me in these. This is my bathing suit that I wear to the beach.

A thinking man (very rare): but your bathing suit is bigger than your underwear, you are naked in public, you are brainwashed.

Girl Today: Oh, you are a crazy.

Quote from: Disputaciones

I know that some catholic schools had pools even before V2, so of course people were swimming in them and this was seen as alright.

Does anyone know how they were required to dress or what the swim wear looked like? Were men, for example, allowed to swim shirtless and in very short shorts?

At Fatima 1917, Our Blessed Mother said:

 "More souls go to Hell because of sins of the flesh than for any other reason. "
"Certain fashions will be introduced that will offend Our Lord very much. " "Woe to
women lacking in modesty".

Those fashions came into existence like overnight in 1920+-. Young women, called Flappers, started wearing mini-skirts, low cut tops, two piece bathing suits, and whoring around town. If you watch old movies on Youtube, you will see the fashions and the brainwashing by Hollywood. This immodesty did not happen in the 1960's, it goes back to 1920+-.

With regard to the beach, I have pictures of my grandfather in 1920-30's wearing what would be described today as Under Armor Boxerjock's. He looks ridiculous.

People can be convinced of anything.

Girl today: This is my underwear, I only let my "boyfriend" see me in these. This is my bathing suit that I wear to the beach.

A thinking man (very rare): but your bathing suit is bigger than your underwear, you are naked in public, you are brainwashed.

Girl Today: Oh, you are a crazy.

I did research the modesty issue a couple years ago, and I knew that yes, it did start in the 1920's.

I have also seen the Fatima quotes in many different places, but only one viable-looking source, and that was a book by a priest. I haven't gotten around to buying it yet.