Well, there is one of Rarity wearing Twilight's swimsuit/tankini and a custom bikini and Fluttershy's wetsuit and custom one-piece swimsuit.
Links:
https://derpibooru.org/images/3175101
https://derpibooru.org/images/3178382
https://derpibooru.org/images/3185833
https://derpibooru.org/images/3187568
https://derpibooru.org/images/3188734