Rob Gronkowski Shows Back Surgery Scar On Bahamas Vacation

Here's Rob Gronkowski showing he's still got a little football in him after retiring from the NFL -- throwing passes to fans in the Bahamas this weekend ... and showing off the scar from his back surgery.

Gronk and his swimsuit model girlfriend, Camille Kostek, spent Easter weekend right by the beach -- taking in some sun at a fancy resort in Nassau ... it's gorgeous.

Kostek shot footage of a shirtless Gronk playing catch with some kids -- and you can see the scar on his lower back from the procedure he underwent in Dec. 2016 to treat a herniated disc.

Gronk returned the following season and had a monster year -- he was named a 1st Team All-Pro in 2017. Pretty amazing comeback.

But now, it's a wrap for Gronk ... he officially announced his retirement from the NFL back in March and says he's excited for the next phase of his life.