What better way to kick off the swimming pool season than to mix Sin City with Playboy pin-ups and reality stars?

On Saturday, a bunch of famous buxom blondes attended the Sapphire Pool and Day Club 2013 Season Opening party at the Rio in Las Vegas, Nevada.

Coco, above, arrived at the event in a very tight, constellation-inspired mini dress.  She hosted the party, letting loose in a pink string bikini and packing a pistol - water pistol, that is.

She tweeted: "Photo op!! Sapphire pool is a cool place to hang out! All these blondes were here w/me @crystalhefner @PamelaDAnderson @GretchenRossi"

Crystal Harris-Hefner, Hugh Hefner's new bride, looked sensual in a colorful bikini with a crocheted coverup. She was joined on the red carpet by "The Real Housewives of Orange County" star Gretchen Rossi, who sizzled in a pale pink bikini. Former "Baywatch" and Playboy icon Pamela Anderson also joined in on the fun.

Check out more photos from the pool party...