I'm reading the Bombshell Manual of Style right now, which is quite a good read, if you want to know what makes bombshells tick.
#1 on her list of must-haves for a bombshell is a "white girdle-front one piece swimsuit, 3 inch ankle strap sandals, and an immense straw sun hat with a ribbon tie. This is not to be worn on the head, but slung over the back and tied at the neck." Sexy.
Her inspiration was Dolores Del Rio, a silent movie bombshell from back in the day. Being a Latina, I'm sure that a white swimsuit looked pretty darned hot, because she'd have a lovely tan. I, however, look sick in white, because I'm as pale as Scarlett O'Hara. So I went on a search looking for the photo that gave the author the inspiration. Alas, I've not been able to find it, but I did find the one at left, which, I'll admit is pretty nice. The viewpoint of the photo doesn't scream bombshell to me, but look at the next couple of examples of how a white "girdle-front" swimsuit can make it work.
The iconic Betty Grable