Ex-'Real Housewife' Kelly Bensimon Looking Hot in a Swimsuit

Kelly Bensimon is one smoking hot mom -- the former model and 'Real Housewives of New York' star hit the beach to prove her hotness is still on point.

Seriously, 50-year-old Kelly went peak MILF when she slipped her rockin' bod into a couple of sexy swimsuits from Melissa Odabash and turned up the heat for a Miami photo shoot.

Check out the gallery ... Kelly wasn't afraid to get down in the sand and the surf. She also did her best "Baywatch" from a lifeguard tower.

If Harry Dubin's looking at these pics ... he's gotta be pissed Kelly's not on his lengthy list of 'RHONY' hookups. Sorry, bro.

The only person NOT hyped about this is Father Time.