Seal -- REBOUNDING with Hot Brunette Bikini Babe

Seal's officially done mourning the death of his marriage to Heidi Klum ... 'cause the singer has moved on to a smokin' hot brunette who looks damn good in a bikini ... and TMZ has the pics.

Just 3 months after Heidi filed for divorce, an extra-sweaty Seal was spotted on a yacht in Italy this week ... gettin' all kissy kissy with a mystery babe after a quick workout session on the deck.

There was cuddling ... there was smiling ... but there was no sign of Seal's wedding ring.

TMZ broke the story, Heidi decided to break off the marriage because she got sick of Seal's explosive temper. The couple later released a joint statement saying they had simply "grown apart."

Meanwhile, Heidi ain't lookin' so bad either ... and made sure the world knew it on July 4th ... when she tweeted out this photo of her insane supermodel physique.

Damn.