LL Cool J -- Half-Naked Pool Party Time

It was 88 degrees in Vegas yesterday -- so LL Cool J decided to beat the heat the best way he could ... with a bunch of half-naked, smokin' hot physical specimen.

Our pals at SpyOnVegas.com caught the rap legend flexing it out at the Wet Republic pool at the MGM Grand.

Sadly, LL kept his shirt on ... but he was basically the only person wearing any clothes.