May Allah reward you for your effort. There are (inside) swimming pools where normally mixing between men and women finds place. Is it permissible for a woman to swim there if they organize a day of swimming with (Muslim) women only? One of the conditions is that women cover up their awrah. May Allah reward you with goodness.
These places are not safe. You can never guarantee that there is no men who can watch.
We have the hadith narrated by Imam Ahmad:
عَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا أَنَّ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: أَيُّمَا امْرَأَةٍ وَضَعَتْ ثِيَابَهَا فِي غَيْرِ بَيْتِ زَوْجِهَا, هَتَكَتْ مَا بَيْنَهَا وَبَيْنَ اللَّهِ” (أحمد)
Narrated by Aisha, may Allah be pleased with her, that the Prophet, peace be upon him, said: “Whichever woman took her clothes off in someone else’s place , she unveiled (broke) Allah’s concealment to her.
The hadith is applied regarding taking clothes off in a place where it is not safe that she can be watched. But if a woman is staying with a trusted friend for example or a relative then it is allowed to do so.