I actually prefer Spandex BBlair Thong Gaffs for a flat femme look, I have posted about them before but have new photos and a new source. This is size M, I have worn this style at crowded beaches, a modest look and it stays on in rough surf. Spandex size M is comfortable for all-day wear, I sometimes wear size S for a nice squeeze feeling. Amazon link
https://www.amazon.com/dp/B08LBQQ1LT/?th=1
My photos of size M