Reply To: Swimming shirts

I know there is a lot of ehrliche yidden and yeshiva boys who swim without shirt and some whith very short swimming pants too, on the other hand in some chassidische camps the boys are required to were shirts and a bit longer swimming pants, although still higher than the knee, it is clear to me that both ways are accepted by the halacha autorities. What i want to understand is that we know that a man should not expose the usualy covered places of his body even when he undresses himself before changing to pyamas at night even when alone in the room. So while a ehrliche yid does cover his upper part and his legs while changing in his private room he exposes them in swimming pool in front of people. There is indeed an exeption for a bathhouse and mikveh because that the derech of washing and toivling, but in which category does swimming pool fall in ? Is it a necessety to swim without at least a thin shirt and thin longer pants ? And especialy when swimming for a longer time and for sport or enjoyment. so, there is my question, why is a swimming pool different ? Anyone with good sources please respond.