Varför har män ”speedos” på stranden?

(US) A tight-fitting swimsuit, especially commonly worn by competitive swimmers and divers. Usually implies a brief or bikini style swimsuit. I could tell that she was a serious swimmer, because every time I saw her at the pool she was wearing a Speedo of one design or another.

• 2011, Gary Ghislain, How I Stole Johnny Depp's Alien Girlfriend‎[1], page 44: She's wearing Mom's teeny-weenie black Speedo bikini, the one Mom wears to show how fit and trim she is.
  
• 1999, Cheryl Rilly, Great Moments In Sex, page 227: These muscle-bound hard bodies are wearing Speedo Lycra bikinis which stick to a man's body like a woman's wet T-shirt.
  
• 2014, Norah McClintock, #3 Dead And Gone, page 12: There were dozens of girls in there - girls on the deck in bathing suits, most of them Speedos because they were racing.
  
• 2016, John Early, Tales of a Modern Nomad: Monks Mushrooms and Other Misadventures, page 59: Ryan and I remain unmoved, standing at the edge of the water as five Speedo-clad lifeguards rush up to us.

(US) (by restriction) A male swimsuit, very tight fitting and small, brief-style, and not a thong-type.

She called down from upstairs, "He'llbe out in a minute: he's just putting his Speedo on."