Following the string bikini thread I went to the beach after work on Thursday and sunbathed for a while in these:
https://www.ebay.co.uk/itm/Sexy-Men-...53.m2749.l2649
Indoors they are navy and a bit plasticy but in direct sunlight they become irradescent reflecting reds and blues. Strangly for something made in China they are larger than you expect so downsize this product.
After work yesterday I swam 2000m in my navy Arena Santa Marias, feely free yet supported in the water while knowing they looked good yet discrete poolside. Am wondering about a pair of Arena Santa Marias in a brighter colour, maybe lime green.