Tom Brady ain't the only quarterback staying in great shape in retirement -- 'cause Eli Manning is lookin' like he's ready to make a comeback ... showing off his solid physique while on vacation with his friends!!
The 42-year-old former signal-caller was aboard a yacht in Portofino, Italy this week ... and he was joined by his old center, Shaun O'Hara, Capital Partners CEO Ben Weprin, and their spouses and friends.
Manning unleashed his inner child as he played with pool noodles, sea scooters, and, of course, a football ... but what really caught our attention -- dude looks GOOD!!!
Now, Manning was never really out of shape during his 16 seasons with the Giants, but the guy hasn't snapped the ball in nearly half a decade ... but it's clear he's making sure he's keeping up with his fitness.
Manning and O'Hara even piggybacked on a jet ski ... proving they're just as close as they were during their playing days.